The SSM2007 Crew recommends
www.nasaspaceflight.com as one of the best (if not THE best) website to keep you abreast with anything-NASA.
There is a very large STS section which is reserved only for L2 registered accounts, but it is worth every cent - if you think of yourself as a Space Shuttle freak or absolutely want to learn more.
Have fun downloading hundreds of Gigabytes of stuff.
/Admin