FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
BirdFont - Birdfont is a free font editor which lets you create vector graphics and export TTF, OTF, EOT and...
draw.io - Online diagramming application
Glyphs - Make everything from dingbat webfonts to full-fledged text typefaces in the most Mac-like font...
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.