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