calibre - Ebook manager, viewer & converter
FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
FBReader - FBReader is an e-book reader for various platforms. Features:
Glyphs - Make everything from dingbat webfonts to full-fledged text typefaces in the most Mac-like font...
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
FontCreator - This professional font editor allows you to create and edit TrueType and OpenType fonts.