Your Draft
YourDraft.com is a very interesting site where you can work on draft versions of documents with others. The site is very aware of users wanting anonymity and the ability to create documents that can't be easily read by the webmaster. Nicely, this means that you don't have to use an email address, if you don't want to, plus each document is encrypted in a way that makes it only possible for you and those you choose to read it.
Depending on which URL you send out to others, you control whether they can edit the document or just read it. There is also a nice clock feature so that you can see when the document was last edited.
This is a very simple and well-thought-out service that libraries and others will be interested in taking a look at.