Brett Favre is showing absolutely no class in this situation. He could easily step up and put these rumors flying around to rest. It wouldn't be that hard.
In my opinion, Favre should stay retired and look into a future as a Quarterback's coach for any team. It'd be nice for Aaron Rodgers to have him come back as the Packers QB coach, instead of as a competing quarterback.
He could even go ahead and become a commentator, I'm sure John Madden would absolutely LOVE to have Favre in the booth with him. He could really use his insight in that capacity, too, as he knows what it's like to play the quarterback in the NFL.
The only plausible reason Favre has to come back to the NFL is to continue adding on to the records that he's set. You can argue that he loves the game, but that's to be expected, he's played it since 1467.
There's a time to call it quits, a time to hang up the cleats for good. I'm not asking him to step away from the game that he loves forever, but I am asking him to let the NFL move on.
As for teams that would be interested in him, the two front runners in my mind are the Minnesota Vikings and the New York Jets.
The Vikings have Tarvaris Jackson starting for them...That's an iffy situation at best. Although the Vikings are going to have a great running game once again this year, they would definitely improve with Favre at the helm, though he'd only be able to give them a year at most. Jackson would definitely improve with some mentoring from Brett Favre.
The Jets don't really need a starting quarterback, as long as they can keep the injury-prone Pennington healthy. He has a good arm and, in all reality, is a good quarterback.
He could easily start for all but a select few teams in the NFL. I'm not sure that Favre could go there and start immediately, as they've already given Pennington the reins to the franchise.
There would be a QB battle, and it would kill Pennington's morale, making it pointless to bring him back next year, leaving them with Clemons at the QB position in 2009.
All in all, Favre should stay retired and spend some time with his family, which he's surely neglected a bit in all of these years.