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...
FontStruct - FontStruct. Build, Share, Download Fonts
Type light - With Type light you can design, edit and convert OpenType, TrueType and PostScript fonts.