At the time of writing, Ainu language and literature is a good example of the sort of learning that is found in books rather than online — but there are some good resources:
Project U-e-peker is a project to make Ainu literature available in English; it contains lots of articles and references to Ainu publications.
Japan Focus has several pages on Ainu topics, including Kyoko Selden’s translation of the intro and first yukar.
Toy Toy for all your musical and artistic Ainu artifacts (Japanese site).
The SOAS talking dictionary of Ainu is good for getting a quick idea of the actual pronunciation of Ainu words.
The Conquest of Ainu Lands is a good large-scale historical overview of the relationship between the Ainu and their neighbors.
アイヌ神謡集辞典 by Hideo Kirikae is an absolutely excellent reference for anyone who wants a general understanding of the language of the Ainu Shinyoushuu. (Japanese language).
アイヌ神謡集を読みとく by Katayama Tatsumine is another, at least equally excellent reference (Japanese language)
Other People’s Links:
Aynu Itak is a fledgling site that contains lots of links about Ainu language. Useful!