Some of our faves, see the [directory.fsf.org Free Software Directory] for lots more cool stuff.

General interest

• Gnugle D.N.E. (yet) but is still an interesting idea, namely a P2P search engine. Could have applications/extensions that would help us out a lot.
• Emacs is software we use (or anyway, some of us do) - and most of us who use it think it is pretty cool. It has lots of packages (email, web browsing, etc., etc.) that make it so you almost never have to leave. You can even use it to edit wiki pages, see RatpoisonWiki:Wiki_editing_with_Emacs, and adapt the instructions you find there.

Math

free alternatives to popular non-free symbolic math applications

(As advertised on Why not non-Free Math.)

These are the main ones:

• http://maxima.sourceforge.net/ computer algebra
• http://www.gnuplot.info/ plotting
• http://www.octave.org/ numerical calculation (matrices, computer vision, etc.).

Look on the LISP page for a link to JACAL. --rspuzio

Domain specific

• PARI is one of the best number theory packages out there, and it is all free. It can also be used as a C/C++ library to compile applications.
• http://www.r-project.org/ Statistics-oriented.
• http://www.gnu.org/software/nana/ Assertion checking (haven't checked it out in detail).