MOBI, For Kindle and Mobipocket ( This format is just like the AZW or PRC yet works on both)
KF8, Kindle Format 8 For Kindle Fire (next generation file format offering a wide range of new features and enhancements)
EPUB, For iPad (Apple iBooks), Kobo eReader, Barnes and Noble Nook, Sony Reader, Adobe Digital Editions, Stanza, BookGlutton etc.
HTML, For Websites or viewing through any internet browser.
FlipBook, Flash books with intuitive page flip / page turn effect for web to be viewed using any internet browser.
CHM, Microsoft Compressed HTML Help
PDF, Adobe Portable Document Format
PDB, Palm Digital Media electronic books
EXE, Multimedia eBooks with virtual turning pages for desktop
HTML5, enhanced html format supported by a variety of new devices and platforms