A growing library of e-books is providing new resources for students and teachers. While your local public library is still a great choice for an actual book (you remember them, don't you? A cover on each side with lots of pieces of paper in between?), the lure of books in an electronic format is strong for Generation iPod. Even for us teachers, there is a lot of value in a text that is searchable, linkable, postable, and bloggable; anything that makes it easier for us to incorporate content into our class materials is a good thing.
Mashable.com is featuring a meta list of free, public domain, e-books that should probably be added to a lot of teachers' bookmarks (or your library homepage). Everything from Thoreau's essay "Civil Disobedience" to Shakespeare's The Tempest can be found with a bit of digging through the list.
Of particular interest to me was a link to the Internet Public Library, featuring an incredible volume of useful references, including an image map resembling an actual bookshelf linking to most of Shakespeare's plays in HTML format.