The most established such tool is FontForge. It started out as something of a Fontographer clone for Type1 fonts only, but has grown considerable sophistication for TT and OpenType as well.

My own fonts, including Inconsolata, are developed using my Spiro tools. The underlying math is quite sophisticated, but the polish and packaging to make it a smooth, easy-to-use app is absolutely not there yet. I will continue to chip at the code in support of those goals, but I expect progress to be very slow unless considerable new energy comes into the project from other collaborators.

See also Dave Crossland’s talk at LGM (audio and video links of the presentation inside that link). There is a bit of information about less mainstream tools on the OFLib Wiki as well.

Best of luck!

FontForge http://fontforge.sourceforge.net/ (that what Raph mentioned) is a tool for developing fonts, free to use and modify under “essentially the revised BSD license”. It is a UNIX type of program, but has builds that work under X11 on MacOSX and Cygwin on Windows.

Also, Adobe, Microsoft, and Apple all have font development utilities they distribute free of charge from their respective web sites. They perform very important technical functions but do not handle design. I haven’t figured out much about them but I’m sure other typophiles are more familiar with them.

Dazld,

you can find some links to font development software (both commercial and free) on my page:

http://www.font.org/software/

Regards,
Adam