Here's game by Discover Magazine which can be both entertaining and educational. Create stars by setting off supernovas in a gas cloud. Level 3 is very challenging.

Bad Astronomy, Good Explanations

Phil Plait's Bad Astronomy website started out mainly as a forum for nitpicking the science in movies (hence the name) but over the years, Phil has turned it into a valuable and entertaining way of educating people about astronomy. Here's a video of Phil answering an intriguing question, "why don't giant clouds of gas dissipate in space?"