Proper Animation is a plugin for for SketchUp Watching the teaser video (below) inspired me to model and animate my very own robotic contraption. This script's premise is that objects in your model--groups and components--can each have multiple positions. You manually assign each position to build an animation. Playing that animation involves using SketchUp's already-existing Scenes feature. The really nice thing is that Proper Animation automatically connects positions to scenes.
The first thing you need to do is download and install the plugin. Its developer is MorisDov; you can find it on his site. Proper Animation also comes bundled with its own tutorial PDF. If you're looking for even more encouragement/inspiration/support, you can check out the plugin's SketchUcation thread.