When watching pre-recorded sessions from technical conferences, I like to speed them up. Usually I can speed up things to 1.5x to 1.8x speed and still understand what's going on. I was able to speed Matt Gemmell up to 2.5x and could still understand him. Amazing. Quicktime 7 had nice A/V controls to speed up the video. You can download Quicktime 7 and use its player.
Quicktime X's player doesn't have an A/V controls window, but you can option-click the fast-forward button to increase the speed by 0.1x. Keep clicking to go faster. Unfortunately you can't pause when sped up, so if you pause, you have to re-click to your desired speedup.