Newbie looking for a simple 2d animation programme

Hi there,

I've recently got into doing short 2d animations, but have so far only been using Windows Movie Maker. my most recent effort can be seen here: http://www.youtube.com/watch?v=3WrDV_u6eR4 to give you an idea of the level I'm at.
The thing is, I'm hink I might be about ready to movie beyond WMM. I don't have grand ambitions to make really complex stuff, I'd just like to make 2D limited animation style stuff, which WMM is largely okay for, but it lacks some features I could use sometimes: like more controlable pansand zooms and the ability to track characters as they move, that kind of thing. What I'm really looking for is something as user friendly and simple to use as WMM but with a bit more features and suitability for 2d animation. Anyone have any suggestions?