Computer Science (Data Mining, Machine Learning):
- Hard science book like PRML from Chris Bishop or Neural Networks from Haykin
- Fun implementations from Programming Collective Intelligence by Toby Segaran
- See practical implementations by these people: http://www.doloreslabs.com/
Statistics:
- Good foundation of probability theory and calculus
- Understand these slides: http://www.autonlab.org/tutorials/index.html
Visualization (something I'm working on but not good at yet):
- Check out http://processingjs.org/
- Dabble in Adobe Flash/Flex Framework