draw.io - Online diagramming application
BirdFont - Birdfont is a free font editor which lets you create vector graphics and export TTF, OTF, EOT and...
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.
FontCreator - This professional font editor allows you to create and edit TrueType and OpenType fonts.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Glyphs - Make everything from dingbat webfonts to full-fledged text typefaces in the most Mac-like font...