I personally like Hash's Animation Master. It runs on OS9, Windows (in case you are collaborating with a Windows person), and is shortly going into Beta for OSX. It has a nice modeler that is spline and patch based...i.e. no polygons to worry about, thus smaller model files, and works well for both mechanical and organic models. It has an excellent animation feature set, and tools that are typically found in higher end (Maya) packages, and sometimes, tools the big boys don't have yet (AM was the first to offer non-linear animation and reusable actions).
The renderer is pretty sweet too, and no offers photon mapping. Plus, most everything you need is built in and you don't have to buy plugins for cool fx and stuff. And, there are a lot of FREE plugins from the AM community, plus an awesome email List service.
AM is used in movies, videogames (Tak and the Power of JuJu), commercials, TV shows, music videos, and so on.
All this for $199 bucks, and that installer CD works on both platforms.
Check it out at
http://www.hash.com
Hope that helps!