I've begun using a 3D program called Art of Illusion. It's fairly full featured, and is pretty mature from version 2.5.1.

It's a little unusual in that Art of Illusion is a Java program - you'll need the Java runtime. You'll want to make sure you have Java installed, and updating to the latest version speeds up performance significantly.

The program imports some popular formats, like 3DS and OBJ, making many of the models available on sharcg  usable.

Although I haven't used the animation feature, it does animation as well as 3D stills. Since it is free and extensible through scripting, you may want to check it out.

Edited by D856C on 03/19/08 10:34 AM.