Free Scientific Software for Developing World?

FlashBoltzmann asks: "I'm a physics student in the US working with a group of physicists, mostly from Africa, who are interested in helping their colleagues on the continent obtain free software for scientific and educational use. Often, many science departments in Africa have little or almost nonexistent funding to purchase new software packages, especially for scientific research or education. Some know of the free software available but say it takes up large amounts of time over often slow internet connections to find and obtain it. I am asking for any recommendations on freeware or open source software, for any operating system, that anyone knows about. We are looking at the Debian version of Linux for a lot of the great software that comes with it but resources for MS Windows would be helpful as well."

"Free educational software of any level is appreciated though we prefer college and graduate level software. Also, field specific software is great, e.g. software for condensed matter physics. Eventually we'll probably combine the software on CDs to be distributed to these scientists. Any help is appreciated especially with programs that perform simulations, mathematical and statistical analysis and plotting, compilers, lab software, etc. The users of the software will most likely be physicists or mathematicians."