SAGE, as seen on Slashdot and Digg, is a mathematical modelling and computation tool. I’ve never used Mathematica or MATLAB so I don’t exactly have a need for this but I’m sure someone may get some use out of it. It uses Python as its scripting language so it should be easier to extend than using a custom language.
I’ve recently been looking into new Linux desktop torrent programs to possibly use as a replacement for Azureus. Deluge is the first one that I looked at and, overall, I’ve found it to be satisfactory and is well worth considering if you’re after a native Linux client.