I would put them like this:
Favre - 3 out of his last 4 matchups are good with the exception of week 17 being against Chicago. He has SF, Detroit, and Minnesota in the next 3 weeks, all have had problems slowing down the pass. He is having a pretty good year and he should be solid from here on out.
Kitna - Has 2 good matchups and then 2 pretty tough matchups to end the year. Plays Minnesota and Green Bay in the next 2 weeks who both struggle defensively and then has Chicago and Dallas to end the year. He has shown that he can put up reasonable numbers even against tough competition however and one can never count out the influence of the Mike Martz offense. Also, they should be getting KJ back for the end of the year.
Grossman - People may be upset with him for being so inconsistent, but with his end of the year schedule, he still is the 3rd best QB listed. He has STL, TB, DET, and GB left to play, 4 good matchups and so even though he carries significant risk, none of those defenses are really that scary.
A. Smith - He's basically ahead of Losman because of schedule to end the year. He has the following left to face: Green Bay, Seattle, Arizona, and Denver. Denver is the only one I would really worry about here, all three of the other have had troubles defending the pass this year. He certainly has some weapons at his disposal so he's not a terrible play if you had to use him for the rest of the year.
Losman - Inconsistent and not the best schedule to end the season. He has a good matchup this week against the Jets, but then faces Miami, Tennessee, and Baltimore. Tennessee may not look great on paper, but they have been playing very well lately including a win over Indy last week. They wont be an easy matchup for him. Just not a good option at all.