There's a new player in town as far as e-book readers for the iPhone. It's called Eucalyptus and after finally getting approved by Apple, it is receiving lots of love on the internets.
It uses the Project Gutenberg etexts, which it reformats beautifully on the fly. Definitely mentioning. However, it's not for me. I'm most interested in readers that can make use of etexts that I create myself. I can dump articles or commentary chunks I have for instance in my bible software, and take them to read on the go.
Side note: Should we settle on etexts, eTexts, or e-texts? ... ebooks, eBooks, or e-books?