I'm not currently running a spare. I have an air pump that has tire sealant that I stole out of the back of my camaro when I sold it. None of the current muscle cars have a spare because the brakes are too big for one to be mounted. Instead they come with a nice little air pump that plugs onto an accessory outlet and gives the option of just air, or air/sealant. The sealant supplied is a non-corrosive type that works great on small and medium punctures. It's nothing that would help if you got a REAL flat, but will work in a pinch.
I do plan on mounting my spare once I get back from vacation....