Firefly I feel strongest about.
Better off Ted, Arrested Development, Dollhouse. Veronica Mars I wanted to see more of, but 3 seasons was a pretty good run, so I don't feel it got completely shafted. Most recently, Terriers. I was keen on 'Crusade', the Babylon 5 spinoff but it wasn't amazing.
I would have watched more Caprica but frankly the 5min ending Epilogue was the most awesome 5min to happen in Caprica or BSG and might not have been as awesome if dragged over many episodes.
Family Guy and Futurama were great choices for 'uncancellation', it seems like they were success stories so that's nice.
Cancellation-related mishaps:
Babylon 5 was told it was going to be cancelled at the end of the 4th season so they packed everything in to the 4th season and it was good and then the 5th season was shit. Would have been better if they didn't threaten cancellation or just went through with it!
Newsradio should have been cancelled when Phil Hartman died, or better still Phil Hartman shouldn't have died and it should have kept going.