NASA Sounds is another great resource from NASA. It is a collection of sounds from spaceflights and missions, including the sounds of a shuttle launch and memorable words such as "Houston, we've had a problem" and "One small step for (a) man...).
The files are in both MP3 and M4R (iPhone) formats for download.
This could be a fun way to use these sound clips in your classroom as a way to get students interested in the topics. I like NASA's idea of using "Houston, we've had a problem" as an error message on your computer.
It's fun and educational.