Ahh, the joys of C++
After getting frustrated with all the C-style mess of Gtk+'s object-oriented structure, I decided to give Gtk-- a try. I wasn't expecting it to be very complete or reliable, but it's been pleasantly surprising. Just as I wished, my programs are now more elegant, more intuitive, and type errors are caught at compile-time rather than run-time. The documentation is not too bad (no worse than Gtk+ itself) and it includes very helpful tutorials and examples.
An open, cross-platform journaling program.
A scientific plotting package.