FontForge (formerly PfaEdit) allows you to edit outline and bitmap fonts. You can create new ones or modify old ones. It is also a font format converter and can convert among PostScript (ASCII & binary Type 1, some Type 3s, some Type 0s), TrueType, and OpenType (Type2), CID-keyed, SVG, CFF and multiple-master fonts.

This also provides these programs and utilities: fontimage - produce a font thumbnail image; mensis - examine and modify some of the tables in a truetype or opentype font; sfddiff - compare two font files; showttf - decompose a font file into its various tables and display it.