Teams that could want him- In the past, New York has wanted him bad. Boston has shown interest. Los Angeles is certainly an interested buyer too. Baltimore and Toronto, both looking for pitching, could want him. In fact, the list is very similar to Cole's list, so tack on St. Louis, San Francisco, and the Angels. Perhaps other teams could sneak onto his list though, as he's owed significantly less than Cole. With that said, he's still owed, as of the deadline, around $45 million between August 1st of 2014 and November of 2015, in part thanks to a large buyout.
What you have to get back money wise- Obviously, you'd like to get out of this contract entirely if you trade him, but doing so will severely limit your prospect haul. His DL stint, of which he's still on, will also make opposing GM's weary of that. To maximize the prospect haul, the Phillies could have to eat between $10 million and $20 million total. That could change though, if you're dealing with the Yankees or Dodgers, or another large market team.
What you have to get back player wise- If you're moving Cliff, and paying any of his salary, a lot. Even if not, you're looking at 3-4 players, of which at least one should be absolutely blue chip, and at least two ready to play for this team in 2015. All of this is subject though to how much salary relief you get in the end.
The Outlook- While it's very hazy, Cliff will be traded at some point. Cliff Lee is probably not going to be here in 2015, unless something changes. Do they trade him in July, as he comes off the DL, do they go into waivers, knowing his big salary will scare off most teams from claiming him, and move him in August, after a few good starts? Or do they move him in the winter, when you're talking about $37.5 million more owed? I think any of these are possibilities, and one will likely happen.