Just a reminder, I'm not discussing restricted free agents. So LB Shawne Merriman isn't available as far as I'm concerned. It's very unlikely any team will surrender one or two high draft picks and hand out a huge contract on the eve of the 2011 lockout for any player.
While it would seem obvious for the Green Bay Packers to consider a free agent outside linebacker who could provide a pass rush opposite LB Clay Matthews, the free agent period is effectively over at this position. Back in December, they resigned LB Brandon Chillar to bring their payroll up around $15 million for the linebackers currently under contract. I would love to discuss whether to resign LB Aaron Kampman, but it doesn't matter since it's nearly certain he'll be signing elsewhere.
Another reason why the Packers won't pursue any unrestricted free agent linebackers is because there aren't any good fits. The best ones, according to Pro Football Focus and Football's Future, are all better suited inside, or outside in a 4-3 scheme. The Packers certainly don't need another inside linebacker. They need someone to play outside and provide a pass rush. There is the soon-to-be-free LB Joey Porter, but as I mentioned a couple weeks ago, I can't imagine the Packers pursuing him.