250+ Killer Digital Libraries and Archives -- a huge database that can help you find books, articles, and other information online. Great resource.
This is a custom search engine that lets you search for free online books at sites including the Internet Classics Archive, Great Books Online, and the University of Virginia Digital Collections.
Online versions of thousands of books, broken into categories like "Fairy Tales & Mythology" and "Business & Economics." Hurray! Good for mobile media (iPod).