FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
BirdFont - Birdfont is a free font editor which lets you create vector graphics and export TTF, OTF, EOT and...
My Script Font - Make a font with your own handwriting
FontStruct - FontStruct. Build, Share, Download Fonts
FontCreator - This professional font editor allows you to create and edit TrueType and OpenType fonts.
Glyphs - Make everything from dingbat webfonts to full-fledged text typefaces in the most Mac-like font...