Here are some sites of interest.
- Wikipedia - a handy encylopedia
- Freemat - a free environment for rapid engineering and scientific prototyping and data processing. It is similar to commercial systems such as MATLAB from Mathworks, and IDL from Research Systems, but is Open Source.
- GNU Octave - a high level language mostly compatible with MatLab
- GNU GIMP - GNU Image Manipulation Program. It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring.
- Blender - is 3D creation program, free to use for any purpose.
- Terragen - photorealistic scenery generator
- Apophysis - free fractal flame editor
- Mathematics Genealogy Project - check out your mathematics ancestry