There is an interesting platform for machinima. They have a limited range of motions and customization, but they do have lip-synching ability built in to their voice system. The result is a bit more cartoony than Second Life, so it appeals more to the teen demographic. Many companies are doing interesting things in the platform, though, so we'll keeping our eye on it!
If you have machinima or movie suggestions from any MMO, please send them to machinima AT massively DOT com, along with any information you might have about them.