I've just been checking out Scribd and I have to say I like it a lot. Scribd is a web publishing community which uses a tool that looks very similar to Flash Paper to enable users to upload and share documents ranging from single pages to complete books.
There's a really wide selection of books and documents uploaded that you can search through, and if you register, you can also start adding your own documents and projects.
The 'reader' part of the site delivers high quality at quite good speeds and you can also get an embed code so you can add the books to your site or blog and build tasks etc. around them. Here's a quick example of a short document on how to teach poetry:
Adding the embed code to this page took just a couple of seconds and I didn't need to register to get it. You just need to register if you want to upload documents.
If you go to Explore and look through the education section there are at least 1000 books or documents there all of which are free. Some really handy ones on teaching and also quite a few dictionaries including the Dictionary of English Slang.
Scribd is definitely a site I want to spend more time on, might even use it to make an e-book version of my Learning Technology blog.
Hope you find something useful.