Nova has been doing some great stuff lately - I think they realized they needed to step it up after Through the Wormhole began it's awesomeness. The 2nd to last episode was about space and how it is not empty, and the last episode was about the relationship between time and space and the fabric of time. Looks like the next few are going to be good too:
"The Fabric of the Cosmos: What is Space?"
"The Fabric of the Cosmos: The Illusion of Time"
"The Fabric of the Cosmos: Quantum Leap"
"The Fabric of the Cosmos: Universe or Multiverse?"
Quantum Leap should be good, and Multiverse stuff is interesting as well.