The Red Bull Stratos page has a lot of cool interactive stuff showing the jump details:
http://www.redbullstratos.com/
And Wired has some fun nerd math on the speed of sound aspect:
http://www.wired.com/wiredscience/2012/02/stratos-space-jump-can-you-fall-faster-t...
I always thought speed of sound went up with altitude, I've carried that misconception for decades.
