There was a good article in the New York Times today on the effect dreaming has on learning and memory.  The fact that dreaming and sleep are good for learning and memory is commonly known I think.  Their description of how dreaming can help you make connections between memories is pretty cool though.  Your dreams could be your brain re-organizing your memories and what you’re learned and trying to find the connections between them.  Leading to inspiration apparently!  Now I have a good excuse for why I want to sleep 9-10 hours a night.