Pro Football Focus had a good breakdown of the impending free agents in the NFC North. There are a number of good players likely to hit free agency from this group, but most of them are restricted free agents, and those free agents haven't been changing teams in recent years. It's free agency in name only, and I expect that will continue.
There is only one real unrestricted free agent of note this year from the NFC North who is actually in his prime. And I expect he'll be unrestricted in any version of the new labor agreement. DE Cullen Jenkins. One of those rare players in the NFL that can provide an inside pass rush as a defensive tackle.
As valuable as he is to the Packers, he may be more valuable to some team as a tackle in a 4-3 defense. Which means they'd throw a lot of money at him. He didn't hurt himself either by recording a career high while only playing in 11 regular season games. And I don't expect he'll be viewed as injury prone either since he's mostly avoided injuries during his career.
Plus he wasn't ever a huge fan of the switch to a 3-4 defense, and he might want to move on ala DE Aaron Kampman. With the list of truly available free agents likely to be a weak list, as it is in most years, I'm sure some team will be willing to overpay. If there's one thing the Packers have never done under GM Ted Thompson, it's overpay for any free agent.
There is always the strategy of placing the franchise tag on him, and then trading him. I expect they'd have no trouble trading him for something, but asking some team to sign him to a huge new contract and surrender a first round pick might be asking too much. They did it before with DT Corey Williams, but they actually expected to keep him that season. Until the Browns came in with an offer (a second round pick) they couldn't refuse. There is a chance that it could back fire and force them into a bad situation regarding the new salary cap, whenever it's finalized. I'm not sure Thompson would put the 2011 season at any risk just to obtain one good draft pick.