If you would like to read a great summary of what happened to nearly collapse the financial system in 2008, here is the link: http://www.fdic.gov/news/news/speeches/chairman/spjan1410.html 
It is from Sheila Bair, the Chairman of the Federal Deposit Insurance Corporation. A bit technical, but only a bit. After all, this is written for members of a Commission appointed by Congress. Enjoy.