Given Flash's lack of built in collision detection functions I've written an AS3 class that includes many useful and common collision detection methods. From my tests they all work perfectly. Given how much of pain this was to make, I hope other can profit from my code, add suggestions and report bugs if they arise.
Haven't tried it, but it looks like a lot of decent code.
One thing it could still use: comments, and specifically those that help when calling one of the functions. I can't remember the name, but something like /** @param line a line */ function blabla(line):void
Because the code looks great, but it might not always be as clear which function to use at which time
