- GCC The GNU compiler suite, the key to the open source movement!
- Perl A very powerful scripting language particularly useful for text manipulation.
- TCL/Tk Another very power scripting language that supports one of the best graphical toolkits available
- Python Yet another very power scripting language that I plan to move to at some point in the future.
- GSL The GNU Scientific Library, a numerical library for C and C++ programming. Normally, I avoid using libraries because they add code dependence, but the GSL is nicely designed a provides a wide variety of coded/tested numerical algorithms that I do not want to code myself. Note, this code also compiles on both Linux and Mac OS X with completely reproducable behavior, including the random number generators. The documentation can be found here.