Microsoft Font Validator - A tool that evaluates how closely a TrueType or OpenType font adheres to the current font format...
AMP Font Viewer - Jump to Download - Download.
FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
Font Manager - Simple font management for GTK+ desktop environments
Apple Font Tool Suite - A suite of tools for working with font files.
Fonts Ninja - Try fonts discovered on websites in any design software