Open Library is an open library catalog that is editable by even non-registered users. It is striving to create a webpage for every book ever published, which is quite a hefty goal. However, they are doing quite well.
Once you’re registered, you’re allowed to borrow up to 5 eBooks for two weeks each. There is a growing collection of eBooks, primarily made up of 20th century titles. Each title can be borrowed by only one user at a time (just like a real book at a library). The book can be read in a web browser, or in PDF or ePub format.