I'm not sure the EasyBib website actually fits into the Web 2.0 category, but it seems to offer a fine service for free: creating bibliographies in either MLA or APA style.
If you are like me, then you find the details of bibliographies to be a tedious exercise in suffering. Well, suffer no more. Visit www.easybib.com and create massive, voluminous bibliographies that will impress even the most erudite professor.