When Spurrier left for the NFL I remember an article saying that even if he came back to college it wouldn't be Florida. He's already accomplished everything there. He's an ego guy, he's not going to just go back to where he was before.
Washington will probably need a new coach next year. I could see Spurrier going there. Pac-10 school falling on hard times, get to play ASU, USC, etc...
Texas might interest him, like S11 said. QB with a lot of potential who needs tutoring, Texas (the state) produces a lot of high level players like Florida does. He loves rivalries. He would be happier than a pic in slop to add fuel to the Texas/Oklahoma rivalry.
What are some other possibilities? I don't see him going to a school in a lesser conference so it would have to be a BCS conference team.