He might not be available to play until Week 6, which at least gives him a chance to get acclimated to the offense of whatever team signs him but assures that he won't be signed to start (not that anyone would be crazy enough to start him, with the obvious exception of Al Davis, who's crazy enough to do anything.)
The best fit, though, would be for a club jumping on the Wildcat bandwagon to sign him for that formation. Vick was always more dangerous as a runner than as a passer anyway, but version 2.0 of the NFL Wildcat requires someone who can throw the ball, not just scramble with it. So... who's planning to run the Wildcat, and who needs someone with Vick's skill set to run it?
Miami drafted Pat White specifically for that role, so they're out. Jerry Jones seems to have learned his lesson about reclamation projects, and the Cowboys have Felix Jones anyway. Chicago said they were going to add it in to some extent, but the Cutler trade probably scrapped that notion. Can't see them emphasizing the Wildcat much. The Eagles brought in LeSean McCoy, who ran it at Pitt. The Chargers have Tomlinson. Tennesse might use it to get Vince Young involved in the offense again. Baltimore has Troy Smith. Heck, even Oakland has McFadden, another Arkansas Wildcat vet. And Atlanta... uhh, no.
The best fit for Vick would be a team who has an established starter at QB, so there's no question of Vick competing for that role, and who plans to add in some Wildcat plays but doesn't really have anyone on the roster who can really execute it. That seems to leave three main options:
St. Louis - the Rams tried the Wildcat a bit with Steven Jackson taking the snaps, but don't have anyone to really be a duel run/pass threat. And Bulger's backup right now is Kyle Boller, with Brock Berlin as the #3. Neither are exactly indispensible.
New England - now this is an interesting idea. The Patriots got torched by the Wildcat the first time they faced Miami last season, and while they stifled it in the rematch that embarrassment got Bill Belichick's wheels spinning. With Matt Cassel earning the big bucks in KC, Brady doesn't have an established backup, and Belichick isn't afraid of looking like a genius by giving talented ballplayers another chance (see: Moss, Randy).
Cleveland - the Browns used Josh Cribbs in their Wildcat last season, who's all run/no pass, and while it would seem they have a glut at QB what they have are two #1's in Brady Quinn and Derek Anderson. If one finally gets dealt, Vick could make sense as the veteran backup/Wildcat specialist. Plus, Bill Simmons would die of some rare aneurysm/hard-on combination if Vick played his home games in the Dog Pound, so really it would be a win-win for everyone.
(Cross-posted to RotoSynthesis).
UPDATE: I've been reminded by my good friend Stevie Robot that Cribbs was a college QB, even though the Browns didn't have him throw much last season in the Wildcat (Cribbs was just 1-for-4 on passing attempts). That likely rules out Cleveland as a Vick landing spot.