I have published a project on CodePlex, ePubLib. ePub is quickly becoming the defacto standard for e readers, and after getting my hands on a (used and cheap) Sony Pocket Reader I wanted to be able to create documents to put on the device.
The format isn't particularly complicated, but there are a lot of little things that have to line up. This library makes it extremely easy. Create a Book object. Create 1 or more Chapter objects. Add the Chapter to Book.Chapters. Call Book.Save(). You can do the same thing for images as of the commit last night. The only knowledge that's required is basic XHTML skills and .NET to use the library.
I also wrote a utility to log me into The Economist's web site (I'm a paying subscriber) and scrape the Print Edition. It works great, a proper TOC, all of the articles and all of the images. I don't think I can upload that source to CodePlex due to perceived copyright concerns, but drop me a comment if you're interested.