The internet is an invaluable tool in modern day research. Collected here are some on-line resources that I have generally found useful as reference and pointers to more comprehensive treatments.

"I think the next century will be the century of complexity. We have already discovered the basic laws that govern matter and understand all the normal situations. We don't know how the laws fit together, and what happens under extreme conditions. But I expect we will find a complete unified theory sometime this century. That will be the end of basic theory. But there is no limit to the complexity that we can build using those basic laws. This complexity can be biological or electronic". -- Stephen Hawking in an interview, Unified Theory Is Getting Closer, Hawking Predicts, San Jose Mercury News, January 23, 2000.