I great place to start poking around would be the Picture Galleries on this site. If you click the link to those at the top of this page, it'll show you galleries broken down by year. Within each year, you'll find another subcategory named Robots and, within that, a subcategory for CAD drawings.
Those are just screenshots, so you won't be able to get inside them and move around, but they'll give you a good idea of how some things work. If you have questions about any of them, you can start or go to a thread about the photo as well.
I can see what I can do about getting an archive together of the drivetrain we're prototyping now. I modeled in Solidworks, so it may take me a bit of time to go in and convert all the parts and assemblies into something Inventor can handle. I'll attach some screenshots of it for now:
