Parts which conduct electricity through a rotating shaft
The part you are looking for is called a "slip ring".  Basically, its a brush on a conductor.  There are also optical slip rings for digital signals that are some sort of fancy arrangements of optic fibers brushing up against a fancy marble.  

If you end up using slip rings, try to make them servicable.  I hate having to spend days dismantling and reassembling big machinery to essentially replace a brush.