FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
AMP Font Viewer - Jump to Download - Download.
BirdFont - Birdfont is a free font editor which lets you create vector graphics and export TTF, OTF, EOT and...
Font Manager - Simple font management for GTK+ desktop environments
Glyphs - Make everything from dingbat webfonts to full-fledged text typefaces in the most Mac-like font...
What Font Is - Find any font from any image (commercial or free)