A great package for drawings in LaTeX documents
It seems that I will stick with xfig for many years to come. This is a superb piece of software and quite handy for drawing graphs (the mathematical objects that consist of "balls" and "lines").
Diagrams are easier to produce with it than with other software that I tried (e.g., Inkscape).
And that's not to mention the plain text file format that is easily understandable.
An open, cross-platform journaling program.
A scientific plotting package.