Use the scripts 'tools/fontgen2' to convert a TTF file into a FON file (it will print the results to stdout, just redirect it into a file).
It uses the NetPBM suite of programs to do all of the work. You can probably adapt it to use something else if you have another graphics package.
Make sure to check in both the TTF and FON file for tracking purposes. Also sometimes we have to hand edit the FON file, pixel by pixel (more fun right?), to get it to look right.
Brian