Would expect Indy and New England to be interested. Indy's got a very good team already, and NE will be better when they get some of their players back from opt-outs, injuries, etc. Both teams have cap space. For New England, I don't know how much appetite Belichick has to build again with a young QB. Given their draft position this year, Stafford might be the better option. Stafford's got quite a few years left in him, barring injuries.
Broncos are coming from a worse position, but they've got some great weapons (Sutton, Jeudy, Fant, Patrick, Hamler, etc). Could be another interesting spot.
EDIT: Forgot about WFT.
Niners too, if they want to move on from Jimmy G.