The companion book to the Doctor Strange comics, by Cat and Nagasiva Yronwode.
An online bookstore catering to all things occult and all paths. Especially interesting for its selection of left-hand path texts. A good site that brings lots of different books together so you can find the non-mainstream texts out there.
A wiki maintained by the Myriad about all things occult, strange, weird, magickal, and unusual.
A wiki full of weird stuff, conspiracy theories, and strange happenings to inspire scenarios in your tabletop or live-action RPG.