This is a great site that provides a free flow of books. Mostly classical literature, it also includes some modern classics for downloads. Started in 1971 by Michael Hart, the Gutenberg Project has grown by leaps and bounds with help from many volunteers around the world. Check out the site and you'll find that there are many ebooks online perusal. It comes in the form of ebooks or etext.
The books available online include classis from other countries and in their original languages. Didn't managed to check if all includes an English translation so you're on your own. Some of the books online are from Germany and China. Mirror sites are mostly at universities which makes contributions to this massive project.
They also call for volunteers to help with proofreading of text here. If you are interested to help out, read this article first. Proofreading is done online though so take note. A dialup connection is fine, for me that is. Not that I use it a lot.