Pioneers of Television" is a great PBS show that goes over the early history of television, showcasing different types and genres of shows; late night, sitcoms, etc. Tonight they're starting their second season, with the theme being science fiction. It should be most entertaining; lots of original Star Trek actors, as well as other early sci-fi shows like Lost in Space, Twilight Zone, etc. I hope they go into some of the very old shows, like Captain Video and Space Patrol, because that's an era I know very little about.
If you're an aficionado of the genre, or of early television in general, I highly recommend this series. As they say in the biz, check your local listings.