iPhone or iPod Touch

Reading applications:

eReader - website / iTunes app store
- PalmDoc, eReader formats
- Simply visit http://manybooks.net/m/ using Safari on your device, and click the eReader download link -- the book will be transferred to the eReader application.
BookShelf - website / iTunes app store
- PalmDoc, Mobipocket, Plucker formats
iSilo - website / iTunes app store
- iSilo, Doc formats
Stanza - website / iTunes app store
- Many supported formats, can be used in conjunction with a desktop application to transfer files. Manybooks supports direct download of EPUB documents from Mobile Safari using the epub:// URL scheme (just click the link and it will download to Stanza on your iPhone or iPod Touch). Even better, browse manybooks.net/m/ from within Stanza!
FileMagnet - website / iTunes app store
- While not technically an eReader it does support Doc (RTF?) and PDF formats. Requires the use of a Mac OS X only desktop application.
BookZ - website / iTunes app store
- Works with plain text files -- manybooks will link to Project Gutenberg, where possible, for plain text versions.