What does science fiction have to teach about real science?

We hear all the time that science fiction inspires scientific work, from satellite technology to genetic engineering. But can science fiction actually teach science to the uninitiated? Authors like Neal Stephenson and Nancy Kress have used their novels to explain astrophysics and biology respectively; Ursula Le Guin's novels feature participant observer anthropologists, while Greg Egan's characters are notorious for delivering science lectures. It may be fun, but are we actually learning anything?

Tomorrow I'll be talking about this on a panel at the Science Online conference with writer Jennifer Ouellette (Physics of the Buffyverse). Specifically we're discussing how to explain scientific topics using examples from science fiction. I tried to do this recently, in my article "The Evolutionary Biology of Star Trek," and Oullette wrote about science lessons from SF in an article called "When Science Meets Fiction," on her blog, Cocktail Party Physics.

What are some examples of science fiction that's taught you about science? What about science books and documentaries that have used science fiction well?