I recently began hunting for a good, free screencast utility that works with games so I can save some replays from an older RTS that doesn't have the option built in. I was beginning to grow frustrated because all the software I had tried, with the exception of FRAPS, didn't work with games and gave me a black screen on the recordings. FRAPS isn't free, and the demo version only lets you record 30 second videos. Then I found something really kewl!
Screen-O-Matic is an entirely web application that works extremely well with my games. Give it a try! ^_^