Graphing Resources
3D Calculus Plotter produced the surface at left (requires Java)
Desmos: explore 2D plotting
Programming Resources
Sage: a free, open source, Python based mathematics software
MiKTeX: free software for typesetting mathematics
To get started drawing tikz pictures in LaTeX documents, like the, check out my favorite Tikz reference.
Websites you might enjoy
Lior Patcher's blog
XKCD, a webcomic
More to come!