Free software for physicists

There's a lot of free software available on the Web for academic and technical purposes. In the absence of anything better to do, here's a list of the stuff I'm aware of and rate as being worth a try.

First, though, some pointers to bigger lists on Wikipedia:

Drawing Feynman diagrams

There are many ways to draw Feynman diagrams. Often the difficult bit is making the associated text labels fit in with the text in the bulk of your text. If writing in LaTeX, the best approach is often to create the diagrams from TeX primitives, using macro packages. Otherwise, there are standalone packages (and there are always vector graphics packages, though you may find boson lines hard to draw). Within the LaTeX solutions there is still freedom of choice between the graphics geometry-oriented approaches and the appealing approach of constructing the diagram from a specified topology.

Statistical analysis

Plotting

Diagrams

These are all drawing packages of the point and click type. If you want programmatic diagramming, which might be useful for mathematical diagrams, then there are plenty of approaches: PyX and Tioga above, are viable options, as is Cairo (through the Python or Ruby APIs, for example) and finally writing Postscript by hand, which is more fun than it sounds (see Bill Casselman's excellent "Mathematical Illustrations" book for more information).

Maths (symbolic algebra)

Documentation

LaTeX is the obvious one here, but for many purposes such as technical documentation there are other, arguably better, tools.

Presentations