There was that one show that came back for another season after fans sent peanuts in because it was canceled. It didn't come back after the second season, but they managed to get it picked up for a season longer then what it was going to have.

Chuck was picked up after some campaigning for the show when it looked like it was going to get canceled(unfortunatly last season wasn't as good as the previous two but we got another season lol). And Firefly got a movie, and I think there's a comic piece coming out or something like that.