A to Z of Ancient Ireland
http://home.iprimus.com.au/selliot/ireland/a_to_z_of_ancient_ireland.htm
A mini-encyclopedia based on the book Ancient Ireland: The Users' Guide by Conan Kennedy. There's some interesting reading here, but some of his ideas are, shall we say, rather unique. And sometimes unintentionally humourous. Take it with a grain of salt.
ADF
http://www.adf.org/
Ár nDraíocht Féin, the neo-druid organization started by Isaac Bonewits. Not really exclusively Celtic - it's based the odd and somewhat paradoxical concept of "pan-Indo-European Druidism". Contains details on the organization, their very intensive training program, and a collection of rituals and articles from past issues of their journal Oak Leaves, which are for the most part a fair bit more in-depth and academically sound than most neo-pagan writings. Even if you find the idea of Greek and Norse "Druids" a bit wonky, the articles are well worth checking out, and at least some of the material is Celtic focussed.
Animal Symbolism in Celtic Mythology
http://www-personal.umich.edu/~lars/rel375.html
An academic paper by Lars NoodÈn, a student at the University of Michigan. Not very long, but an interesting read and well-documented.
Celtic Twilight
http://www.celtic-twilight.com/
A compendium of Celtic myths and legends, albeit with the unfortunate additions of a lot of advertising, and music playing on every page. On the main page, it's sort of an elevator-music version of a Nine Inch Nails song, which is kind of surreal. There used to be a complete copy of Lady Charlotte Guest's translation of the Maginogion on here, but it seems to have been removed. Copyright issues, maybe?
Conrad Bladey's Irish Studies Pages
http://www.ncf.carleton.ca/~bj333/HomePage.home.html
A big, sprawling site with information on pretty much all things Irish. Of particular interest to Celtic pagans is the folklore and seasonal celebrations section, of course; and also the sections on Irish tales; traditional crafts; food and drink; and music, song and dance. There's also an appealingly dry sense of humour throughout - I especially liked the "Irish Page Counter" on the main page...
Cornish Folklore on Gandolf.Com
http://www.gandolf.com/cornwall/
One of the less well-known ofthe "Six Celtic Nations", Cornwall has its own rich folklore... A sizeable collection myths and legends, categorized by theme (fairies, giants, places, etc.).
IMBAS
http://www.imbas.org/
IMBAS, an international Celtic Pagan organization (of which I'm on the governing council - obligatory conflict-of-interest alert), started out as an Internet mailing list, but is now a real-world organization with a quarterly journal, a correspondence study program, and occasional in-person gatherings (well, only one so far...). The evolution of the organization has been a bit of a rocky road, but things are still progressing. The web site has a ton of information, including a library of articles and a recommended reading section linked to bookstores in both the US and UK.
Molly McGinn
http://www.geocities.com/Athens/Delphi/4715/
The site has no title, so I've just named it after the author, who was formerly known as Molly Ní Dana in Celtic reconstructionist circles. The most noteworthy features are the entire text of Nora Chadwick's classic book Imbas Forosnai, which makes the site quite well worth the "recommended" designation all by itself, plus detailed information on shoes and clothing of early mediaeval Ireland.
OBOD: The Order of Bards, Ovates and Druids
http://druidry.org/
One of the oldest neo-druid groups, based in the Celtic Romanticism of the 18th-19th centuries. Like the Romantic movement in general, it's based more on poetry than history, but that's not such a crime, in my opinion... Contains detailed information about the order, and an interesting interactive "magical journey".
Shining Lakes ADF Grove
http://www.shininglakes.org/
ADF info from a grove in Ann Arbor, Michigan. The site has grown tremendously over the years and now includes a massive collection of rituals, plus articles, song parodies, information on various guilds within the grove, and more.
Technovate.org
http://technovate.org/web/
An eclectic site, though more Celtic than not, run by Ray White, a man who, as I've said elsewhere about Rowan Fairgrove, is involved in so many things he's got to have discovered the secret of a 28-hour day. This site hosts several mailing lists including the venerable Nemeton-L, and also includes online Ogham readings, information on the Coligny calendar and more.
The Henge of Keltria
http://www.keltria.org/
The Henge of Keltria evolved out of ADF, but has a more strictly Celtic, and more mystical focus. They at least at one point published an excellent magazine entitled Keltria: Journal of Druidism and Celtic Magick, but the last issue referenced is Lughnasadh 1998 and the site itself does not appear to have been updated since 1999. Still, there are some articles available online, so it's worth exploring.
The Sanctum of Cathbad
http://www.wildideas.net/cathbad/
An excellent site - home of the well-known (and frequently plagiarized, unfortunately - a number of sites have posted it without linking back or even crediting the author!) Solitary Practitioner's Druidism FAQ. Also includes selections from the Carmina Gadelica, interesting material on philosophy, and much more. Now relocated to this very server, since the author lost his web space at the University of Guelph when he moved to Ireland to do his PhD there...
The Summerlands
http://www.summerlands.com/
A wide-ranging site created by Searles and Deborah O'Dubhain, focussing on Celtic paganism but with diversions into healing, magic, men's and women's mysteries, and more. They do have a paid membership structure, with most of the site being only accessible to members, but the price is low, and from what I've read of Searles's work, the quality is probably high, so I think it's probably worth it...
Theology for Pagans
http://www.geocities.com/pagantheology
The title is a bit of a misnomer, as theology is only one of the topics dealt with on this site, but what there is on the topic is quite good. The site also contains a number of primary texts on Celtic mythology and folklore, a paganized Carmina Gadelica, and a number of interesting tidbits including an article on divination via Google for technopagans. Well worth checking out.
Tir na nOg - The Virtual Irish Cybercafe
http://www.alia.ie/tirnanog/
A very funny, but also informative, site. Contains everything from an online transcription of an old text on the social history of ancient Ireland to an amusing piece on the "Partholonian Liberation Front".
