I figured most people here would enjoy this topic. A lot of tv sets are reused on other tv shows. The saved by the bell hallway is a very commonly reused set. I think it is the hallway on iCarly now and I have seen it in a lot of other shows, movies, commercials, etc. The high school on Buffy was the same as 90210 and many other shows.

Anyone have anything else?

I noticed back in the 80's/90's, when they'd shoot pilots of new series that eventually made it to air, that they'd use different sets during the pilot that were of existing or just-cancelled TV series. The pilot episode of "Family Matters" uses the set of "The Hogan Family." I can't remember specifics of other series, but I remember the pilot episode of The Cosby Show used a different set, as well as Beverly Hills 90210. Don't know if they used from other shows though. I think some other shows used different sets for their pilot episodes but can't remember specifically right now.

If you look closely at some of the outdoor scenes on "Dawson's Creek" and "One Tree Hill" you might notice the same town area since both shows are filmed in Wilmington, NC.

The Thomas' house on What's Happening was actually the Sanfords' house from Sanford and Son minus all the junk.

"Hangin' with Mr. Cooper" used the "Growing Pains" in the first episode and even played off the fact by having Alan Thicke make a cameo appearence.

The Chicago high-rise kitchen in Susan Harris' short-lived sitcom "It Takes Two" was reused for Blanche's Miami rancher in her much more successful series "The Golden Girls". You can peak it in the opening credits and see it fully around 4:10: