BTW, there is now a Gtk-based version of xmbdfed, with basically the same interface but using Gtk instead of motif.
Have a look at xmbdfed, a Motif (LessTif) based font editor - while Motif isn't the preferred GUI toolkit anymore, this editor has a number of very useful functions (both UI-wise and code-wise); for example it can import a large number of font formats (e.g. TeX ones). AFAIK, it is still being actively developed, so it may be a good place to look for collaboration opportunities.
An open, cross-platform journaling program.
A scientific plotting package.