GdkRgb is a rewrite of the image rendering subsystem of Gtk+. Advantages over plain Gtk+ 1.0.x include higher speed, very smooth and pretty dithered modes, and support for more displays and visuals. It is currently checked into development versions of Gtk+ (and used in the development tree of the Gimp), but is also packaged separately for application authors who want to maintain Gtk 1.0.x compatibility. The programming interface is quite simple.
Genius is an arbitrary precision integer and multiple precision floating point calculator. It includes its own programming language similar in some aspects to C, bc, or Pascal. It can deal with rational numbers and complex numbers. It has matrix support as well. It uses the gmp library so it is very fast for calculations of large numbers. It has a command line and a GNOME interface. The GNOME interface supports plotting functions and 3D surfaces.
George is a file reorganizer and CD creator, especially suited for the creation of MP3 archive CD's. It will take files from all around your system and/or network, organize them into somewhat lexicographically sorted CD-sized chunks and provide means to create CDs using external pre-mastering and mastering software. George is written in perl, using the gnome-perl and Glade-perl modules (amongst others). There is also a command-line version of George which does not need any special (non-standard) Perl modules. To actually create CDs with George, you also need recent versions of cdrecord and mkisofs.