Atwood's ownsite has a biography, information about her books, and an FAQ, among other sources of information. It's a great place to start learning more about the author.
Another excellent starting point, Atwood'spage at the Academy of American Poets site, has a biography, and links to poems and other web pages. What's different in the nature of the biography here as opposed to the one on her own site?
This is thehomepage of the Margaret Atwood Society's site, maintained by "an international association of academics who study and teach the works of the Canadian writer." You'll find lots of links and some pictures there.