New York Times on MBS/CDO
The New York Times has a great, simple graphic which explains the MBS/CDO process. If you want to fully understand the securitization process, this is required reading. The only missing piece is how the agencies such as Ginnie, Fannie, and Freddie back MBS. It appears to be left out in order to focus on the riskier subprime junk which the agencies will not touch.