Though apparently run by a nonprofit, this site has a very commercial feel - it seems to be primarily a dating site, with connections to a couple of porn sites. But it does also have a (very small) articles section (very small as in only two articles, when I last checked), plus discussion forums and a reasonably decent resources section. They also put out BiMagazine, which I've listed separately as it's a separate site with a very different feel.
Probably the biggest online community for bisexuals, with articles, discussion forums, personal ads, live chat, and more. Rather annoyingly, you have to register in order to access most of the content, and the registration process seems to assume that you're looking to place personal ads, requiring you to indicate whether you're a single or couple, for example. No way of indicating if you're in something like a poly triad, either. However, it's otherwise a good site.
Shamanism: Working with Animal Spirits
I've put this here rather than under shamanism despite the title, because the focus is very specifically on animals. A very interesting site, with an appealing domain name (animalspirits.com), but slow-loading due to the many animal pictures. Over 300 animals are featured here, with photos and brief descriptions of their spiritual significance. And not just the well-known ones, either -- they've got everything from stink bugs to protozoa! One can easily get lost in here and spend hours looking up different animals, although the academic in me wishes they would cite sources for the historic/factual (as opposed to experiential) parts of the information. In the time since I first discovered it, it's expanded to include discussion boards, chat rooms, and much more. Definitely enough to earn the "Recommended Site" designation, even if parts of it are a little more new-agey than I would have liked...
Probably the best intro to Wicca, in the traditional sense of the word, that you'll find anywhere on the web. The Starkindler tradition is an Alexandrian offshoot that is more overtly gay-positive than many traditionalist groups are. The site contains a considerable amount of information about Starkindler, its parent trad, and traditional Craft in general, written in a way that is straightforward and accessible but clearly geared toward a relatively intelligent and well-read visitor.
Wicca for the Rest of Us
A down-to-earth, somewhat irreverent site that positions itself as an alternative to the plethora of fluffy, new-agey Wiccan sites out there, and shoots down many popular myths and misconceptions. Enlightening and entertaining.
The Frugal Domme
A highly useful and entertaining site devoted to practicing BDSM on a budget. They sell inexpensive toys, and also offer a wealth of information on making your own, plus a great deal of general BDSM information, FAQs, humour, a directory of local groups, a message board, etc. A female-dominant perspective, but a lot of the information is useful to anyone regardless of gender or orientation. The site design is overly busy and thus a bit confusing, but otherwise it's an excellent site.
Bisexual Resource Center
Web site of an international non-profit organization dedicating to educating people about bisexual issues. The main page of the site is a news listing, in a blog format, but there's also a very extensive resource directory with hundreds of bi-related links.
A site by two feline therians, divided into personal sites by each of them plus a combined link area. Keller's side of the site, Felinity Reclaimed, contains essays on therianthropy, spirituality, social issues and other topics; poems, and a still-nascent book review section; Kefira's side contains a few essays, some artwork, and several sections that don't yet have much in the way of content, but will hopefully grow in the future.
Kama of Kingston
An interesting site by an Anglo-Indian sex worker who is working to reclaim the Devadasi tradition of Hinduism. Contains interesting views on sacred sexuality within a Hindu context.
Body Modification E-Zine (BME)
Definitely the highest-profile body modification site around there, with a vast collection of stories and photos submitted by members of various body mod procedures from piercing and tattooing to more extreme practices. Also includes an "Ask BME" advice column, an encyclopedia of body modification related terms, and much more. Some of the more extreme content can be a little scary even to those comfortable with things like genital piercings, but those parts can easily be avoided if you're not up to dealing with them.
An online bisexual magazine with a lot of interesting articles and a very international focus, with a number of articles on the status of bisexuals in different parts of the world. Also includes poetry, visual arts and music coverage, though some of these sections still seem to be pretty sparse. The majority of the content is under non-fiction.
A very large and diverse collection of texts on chaos magic and related topics, including digital copies of a number of classic occult texts, a special section on occult swordplay, a wonderful occult humour section called "Banish with Laughter", and more. Probably about the largest collection of chaos information you'll find in one place anywhere on the web, and nicely designed too. Note: newly back online at a new domain, after a lengthy absence.
Beaufort House Index of English Traditional Witchcraft
This family tree of British traditional Wicca, showing the history and inter-relationships between a wide variety of traditions, and with a mini-page on each trad and links to sites by members of that tradition, has now moved to a new host, though it still doesn't appear to have been updated in a long time. Still, there's useful information here.
Desiree's Musings: The Faery Notebook
A subsection of a web site reviewed in the Wicca section, this site differs from a vast majority of other faery sites in that it clearly acknowledges the "darker" and less benevolent side of Faery. Contains essays on typical fairy art, stereotypical faery traits (including some ideas as to why these are associated with faery), and a collection of poetry with commentaries.
The Hermetic Library
This is a huge, beautifully designed site hosting everything from the largest collection Crowley's books I've seen anywhere to Hakim Bey's works on ontological anarchy. They're also coordinating a project to put the entire library of the Golden Dawn online. Any time I start thinking my site's large, I can just take a look over here and be humbled...
A personal site on therianthropy, with essays -- often very opinionated -- fantasy artwork, etc. Very attractive design, though the "mystery meat" navigation takes a bit of getting used to. Includes a FAQ on contherianthropy -- that is, therianthropy without the experience of "shifting", where the animal self is present at all times.
Mystic & Anthropomorphic Feline Lore
Formerly a subsection of the alt.horror.werewolves FAQ (listed separately above) dealing specifically with felines, this site is a collection of myths and folklore about various members of the cat family, from domestic cats to lions, tigers, etc. The fact that it's formatted as one long page make it a bit awkward to read through, but it's well worth the effort.
A directory of therianthropy-related articles and essays on the web. Fairly comprehensive and nicely designed.
One of the larger sites on the topic of therianthropy, with everything from a "were-humour" archive to a listing of European "Howls" (therianthrope gatherings) to articles on Japanese animal lore. Also contains a large index of "werecards" -- little questionnaire-type things that the denizens of alt.horror.werewolves use to describe themselves.
Chas Clifton's Writing on Paganism, Wicca and Nature Religion
One of the very few decent authors ever to be associated with Llewellyn Publications, though he no longer writes for them; Clifton is also an academic; co-ordinator of the Nature Religion Scholars Network, and editor of the International Journal of Pagan Studies. This site contains articles that did not make it into his four Witchcraft Today anthologies due to their "controversial" nature, plus a collection of his "Letters from Hardscrabble Creek" columns which you may have seen in various pagan magazines, and other writings. I especially like "Nature Religion For Real.