I started trying to find useful things to do with face detection, but with limited success. I tried using the Libspark Haar Cascades implementation of face detection with Papervision3D to create a sort of head tracking effect, but it’s a little flaky – partly because of poor tracking accuracy and partly because it’s too CPU intensive. You can view it on its own page here.
I’ve been playing around a little with the online Flash building tool, Wonderfl. If you haven’t seen it already, I urge you to create an account and have a go. You can browse the weird things that people have created, fork other users’ code, or write you own from scratch and see the results compiled online in realtime. It’s a great way to learn graphics coding in AS3 I reckon.