Asatru-U. Great introduction to Heathen concepts and ideas.
Northvegr. Great resource full of texts including some of the vital ones to the lore as well as later myths, fairy tales, and scholarly essays. Highly recommended!
The Door to Uppsala an excellent intro site to Asatru, and a great article on the different factions that exist within Norse Heathenry can also be found there.
The Viking Answer Lady. Everything you wanted to know about how ancient Heathens REALLY felt about things such as blood "purity", homosexuality, and how they conducted their daily lives.
Runes, Alphabet of Mystery. Contains an introduction to the Runes.
The Runic Journey. Another excellent introduction to the Runes.
The Seidr Index. Introduction to Seidr and links to websites and more information about the craft.
Section on Icelandic lore at the Sacred Texts website. Contains the Eddas, the Sagas, modern retellings of some of the lore, all featuring reviews and scholarly commentary.
Exploring the Northern Tradition by Galina Krasskova
Essential Asatru by Diana Paxson
Living Asatru by Greg Shetler
Gods and Myths of Northern Europe by H. R. Ellis Davidson. It was also printed as Gods and Myths of the Viking Age. If you can find it I also recommend The Road to Hel.
The Poetic Edda and The Prose Edda both by Snorri Sturulson. Goes without saying. You should also try to read as many of the Sagas as you can find.
I strongly recommend reading the fairy and folktales of Europe such as the ones by the Brothers Grimm and Hans Christian Anderson as those tales give important clues as to how to interact (as well as what not to do) with landspirits, which is an important element of our faith that is sadly neglected in much of American Heathenry.
Taking up the Runes by Diana Paxson
The Ancient Fires of Midgard by Andrea Haugen. Download it for free here.
Elves, Wights, and Trolls by Kveldulf Gundarsson
Passage Meditation (formerly published as Meditation) by Eknath Easwaran. I know, I know...it's not a Northern Tradition or Norse spirituality book. However the late Mr. Easwaran wrote here a beautiful piece that I think people of any faith can find helpful and practical. There is a lot of wisdom in his words in these pages, and meditation is a skill I personally feel people should try to master for many reasons. He also talks of the importance of slowing down, appreciating others, and maintaining discipline--oh, a Heathen virtue!--among other skills which I think more people should strive to fit into their lives.
The problem with finding information on Forn Sed is that A) Most sites that will turn up if you type the phrase in a search engine are on folklore, which isn't a bad thing necessarily since the spiritual path is based primarily on the folklore of Scandinavia but isn't much help when you're seeking information and help on translating the information into a religious practice and B) Most of the sites that are on Forn Sed aren't in English! Below I have a few resources that will hopefully help and I will put more up as I run into more.
YouTube videos on Forn Sed. Achird1 has done an excellent job on producing informative videos in both English and Sweden on the practice of Forn Sed, the differences between it and American Asatru, and emphasizing the path as a life-affirming, nature-revering spirituality. I highly recommend watching all of his videos, at least the ones you wouldn't need a translator for.
Swedish Asatru Assembly. This site has a fairly good sized section in English with some good articles.
Forn Sidr. Danish website for a Forn Sed organization with another pretty good section in English.
Lokahal. Site run by followers of Loki, and dedicated to providing information and discussion on this complex god.
A Vanic Druid's Hearth run by a friend of mine. Thought provoking essays, devotional material, and others.
Raven Kaldera's site on Northern Tradition Shamanism. Great introduction to shamanism as it applies to the Northern tradition. It's not an Asatru site per se but rather deals with another path of Northern Paganism known simply as Northern Tradition Paganism/Shamanism.
Scandinavian Folklore Blog. More trolls, more landwights, and more good information.
Finnish Paganism. Self-explanatory. May not be Norse but it never hurts to learn more about other cultures and practices, and besides I like the attitudes expressed on that site.
Shadowlight. Page on the Rokkr, the name given to the group of Jotun who are prophesised to be involved in Ragnarok, directly or indirectly, and that includes Loki, Angrboda, Hela, Fenrir, Jormungand, Surt, Niddhog, and a few others. I don't agree with everything on the site but it does provide a lot of food for thought.
Chambers of the Heart. Site on spirit-working maintained by a fellow Northern Tradition spirit-worker and Priestess of Odin.
Ironwood Kindred. Site for a Kindred maintained by it's Gydja, a friend of mine. It's based in New England but has members all over the place.
Gangleri's Grove. Personal website of Galina Krasskova, author of "Exploring the Northern Tradition" as well as many other books and devotionals.
Firefly Pages. Personal website of Silence Maestas, focusing mainly on the use of entheogens in Northern Tradition spirit-working.
Wacian Brun. Site focusing mainly on Vanatru/Vanic worship.
Asphodel Press. Featuring small-market books written by indepedent Pagan authors. Home of Raven Kaldera's "Northern Tradition Shamanism" series which I highly recommend. I'm biased towards the site as well since my devotionals are published through them :)
From the Heart, For the Heart: Devotionals for the Trickster by Tracy Nichols. My devotional, written with the help of other individuals, dedicated to my beloved primary patron Loki.
Full Fathom Five edited by Galina Krasskova. A devotional for the sea Gods of the Norse: Aegir, Ran, the Nine Undines, and Njord. It's a beautiful work and well worth getting, and I'm not just saying it cause I got a couple of pieces in it :) (You can get it much cheaper if you buy it direct from Asphodel Press).
Feeding the Flame: A Devotional to Loki and His Family compiled by Galina Krasskova. A devotional honoring Loki, Sigyn, Angrboda, Fenrir, Jorgunmand, Hela, Narvi and Vali, and many more.
Gifts of the Golden God by Sigrun Freyskona. A devotional honoring Frey.
Odhroenir: Nine Devotional Tales of Odin's Journeys by Laure Lynch. Another devotional for Odin.
Water From the Well and Other Wyrd Tales of Odin by Laure Gunnlod-Hjarta Lynch.
Trickster, My Beloved: Poems for Laufey's Son by Elizabeth Vongvisith. Devotional poetry for Loki.
Love and Shadows by Elizabeth Vongvisith.
A Devotional: Honoring Thor and Family by Robert James Etter
The Whisperings of Woden: Nine Nights of Devotional Practice by Galina Krasskova.
Odin's Gift. Website maintained by Michaela Macha devoted to housing Heathen poetry, songs, and other offerings of the sort.
The Jotunbok: Working With the Giants of the Northern Tradition by Raven Kaldera. Although not a devotional per se I have included it here because it does show the depth of devotion that those who choose to worship the Jotnar possess in their words.
The music of Hagalaz Runedance aka Andrea Haugen, aka Nebelhexe. Although she has ceased to perform under that name, she did come out with some very beautiful devotional Heathen music. Her stuff as Nebelhexe is good too, although it is more ambient-goth.
Freyja, Lady, Vanadis: An Introduction to the Goddess. Not sure if it counts as a devotional but it is a book dedicated solely to Freyja which in my mind counts as a work of love to one's chosen God.
A Journal of Love and Pain is a site run by another Lokean, with most of her poetry dedicated to Hot Stuff.
Root, Stone, and Bone: Honoring Andvari and the Vaetir of Money by Galina Krasskova and Fuensanta Arismendi. Devotional dedicated to the Duerger Andvari, known in the lore as the Duerger who cursed the infamous Ring.
Note: If you are an independant Heathen/Northern Tradition author and would like your book listed or site listed here or in the links section, let me know!
Books to Avoid:
DJ Conway, anything by her--Norse Magick is basically Celtic Magick, just with names switched around, and both books are complete butcherings of the respective cultures' lore. Moon Magick might have gotten rave reviews from most of the Pagan community but when you look into the Deities she speaks of it's clear she knows nothing about it. Her knowledge of Hindu and Kemetic Deities is atrocious to speak nothing of the Norse.
Falcon Feather and Valkyrie Sword is even worse. She calls what she writes about in there seidr...as a seidkona in training I find that offensive. She attributes the discovery of the Runes to Freyja instead of Odin, claims Frey as merely a male face of Freyja made up by patriarchal-subjugated women to make the cult of the Vanir more appealing to the evil menfolk, her knowledge of the Runes is pathetic, and her attempt at fitting the practice of seidr into a narrow modern Wiccan framework is absolutely disgusting. Let's not forget all the male-bashing and the talk of the ancient universal Goddess religion. If a really bad form of Norse Dianic Wicca peppered with bad scholarship and the demonization of anything masculine is your cup of tea, hey go for it. Otherwise avoid this work...and avoid all other works by her too. They're all crap.
Silver Ravenwolf, anything by her--Her scholarship is atrocious, she preaches tolerance yet takes every opportunity to bash Christianity, she encourages teens to lie to their parents, she helps further perpetuate the myth of Wicca as some ancient universal Goddess cult with all Pagan societies being bastions of gender equality (tell that to Pagan Rome, where women were treated far worse than they were even in Medieval Christian times. They were prisoners in their own homes and wives had to walk around veiled to hide the shame of sexuality which they alone carried), bastardizes Wiccan rites (the red at Beltane symbolizes the blood of a girl when she loses her purity. So virgin = pure, non-virgin = ? What decidedly non-Wiccan thinking), her otherall ethics are questionable, she commercializes witchcraft (Teen Witch Kit anyone?), and a host of other things too numerous to say here. Just stay away.
Ralph Blum, anything by him--Blank Rune. Need I say more?
Rites of Odin by Ed Fitch--Again with fitting Nordic beliefs into a narrow Wiccan framework, and badly at that.
Edward Thorrson--while his knowledge of the Runes is pretty good and he's considered the definitive authority on the subject just about, I don't trust his other stuff. The Hammer Rite is pretty much a ripoff of Golden Dawn style ceremonial magic yet he presents it as an ancient Norse rite. His sources are questionable, any footnotes he does provide are his own works, he views the Gods as archetypes to be emulated rather than actual breathing deities. If you read him, read with a critical eye.
Another one to read with a critical eye and extreme prejudice is Freya Aswynn. Her Runic interpretations can be questionable to say the least and there are a few other issues I have with her material that I'm sure other Nordic types can agree on.