Usability 
MobileRead is a very active blog and forum dedicated to getting and using eBook and Web content on mobile devices.
Lots of good items about ebook readers formats and ebook sources. Tips on how to "convert books to different mobile formats. The focus is on dedicated readers like the Kindle but there is also discussion of eBooks on phones and PDAs.
Mobileread also has a library of about 1000 ebooks available for download. Source: Mobility.mobi