My preferred OS is since 1998 Debian GNU/Linux.

An impressive collection of codes: http://people.sc.fsu.edu/~jburkardt/.

http://www.maths.lancs.ac.uk/~ribeiro/geostats.html- Something about Geostatistics (geostatistical R  http://www.r-project.org/ extensions)

Visualization tools


Remarkable Java programs

All programs include the source code.