Comprehensive listing of ebook readers for various ebook formats running on Windows, Linux and OsX.
http://wiki.mobileread.com/wiki/E-book_software
The Mobipocket Reader displays text and graphics and supports Palm doc, txt and html formats. Versions are available for the Palm, Windows Mobile Pocket PC, Windows Mobile Smartphones, Franklin BookMan, Nokia and other phones using the Symbian operating system, the Blackberry, BenQ-Siemens and as a PC desktop reader for Windows.
http://www.mobipocket.com/
The Microsoft Reader displays text and graphics. Versions are available for Windows Mobile Pocket PC and Smartphone, CE, 95, 98, ME, XP, NT, 2000 and Tablet PC.
http://www.microsoft.com/reader/