Thanks to all the users who have helped out with suggestions and bug reports.
The Skiing image is by Kris Arnold, released under an Attribution-ShareAlike 2.0 CC licence.
The Baseball video and screenshots are from Intro to Baseball by The On Deck Circle. They're released under an Attribution-ShareAlike 2.0 CC licence.
The skidiving video used in the introduction is by Gary Roth. Other Skydiving images are by Dave Clarke.
The GoPro icon is from http://www.iconsmind.com
Music for the various tutorials is Acoustic Guitar #1 by Audionautix.com
Video Debrief uses several open source projects which are listed below