I don't think he'll possibly be traded, but if we want to discuss possible destinations
Miami seems realistic; the Jets and 49ers could always be a case, however it would require Ryan/harbaugh to go against QBs they've publicly spent the last few months backing as "their guy", "not looking to replace", and having no problems
other places could include the Seahawks, Redskins, Bills, Browns (if they're not overly sold on RG3)...with a maybe towards the cardinals (can't quite read the franchise's feelings on kevin kolb at this point).
As much as Dallas fans here want it (presumably out of dislike for Romo or want of witten and manning on the same team), it's very unlikely to be a realistic option. Their real hindrance and concern the last few years has been a complete inability to run the ball and so, so many changes needed to the defensive personnel (esp DBs); granted they may have found a running game in Murray (unless that sputtering toward the end of the year before the injury was early indication he's about to pull a Steve slaton)...however the fact that the team before playing him was having to mostly throw the ball when leading and trying to run down the clock was pretty indicative of a problem there). The FO and coaches are too sold on romo to put all their eggs in manning's basket for 1-3 years (though I think manning could realistically play 3-5 more if fully recovered, getting traded out like Montana did feels like it would lessen that number) (...and itd be a poor choice to do so anyways, then expect to have romo or another QB smiling, practiced, and ready to go as soon as he hung it up). Realistically, the cowboys major concern needs to be defense - CB comes to mind - and they're best spending their money there (and they probably know it).
I dont know where the Houston proposition seems to be coming from, but that seems the least likely of all. They have schaub, he does a great job, and they're set at the position...moreso than maybe all but 10 teams in the league. (I have to guess the push for manning here is coming from either the abundance of offensive weapons or that he and foster could be on the same team). Houston's fault was always their defense (which for some reason they refused to work on or fix for years, opting to always improve the offense) and a heavy focus on the running game in spite of not having the backs to do so (as well as in spite of their strength clearly being in the passing game). Having Foster and Tate has seemingly solved that problem. As far as the defense, personnel and scheme-wise (now that wade phillips is their DC), thats seemingly improved in spades. Granted they're one of the teams that might have the fewest offseason needs so they might look for improvement wherever they can find it, but even so that money would most likely be (and be best spent in) further defensive improvement, WR #2, or oline...not to mention bringing manning in to start is just going to cause locker room strife throughout the year (nothing personal to manning), as the FO would be pushing aside not only a guy who earned the starting job and has maintained worthy level of play but also one who many have considered at times to be one of the top 10 QBs in the league.
Quick two more:
Minnesota is very seemingly sold on going forward with playing and developing Ponder the next few years, so that's one likely would not happen.
And the titans arent going to do it either (as much as UT/titans fans would like it). Too many immediate needs on defense (it needs to be improved in multiple areas AND theres a fairly likely chance theyre not resigning any of their 3 starting DBs except Babineaux - strong safety is the position I think they most needed to improve offseason personally). They also need desperate improvement to that offensive line (and if they're not starting locker yet, they're likely fine going with Hasselbeck one more year since they paid him)