It sort of depends exactly which need the Patriots are trying to fill.
They could sorely use a versatile 3-4 OLB who can rush, cover, and set the edge.
They could also use a situational disruptive pass rusher.
Sort of two different roles.
Versatile options:
Manny Lawson - great speed, tall, lean, much lighter than normal Pats OLB's, great coverage (more passes defensed than the next five free agent OLB's combined), in a rotation at SF, improved in 2010
Matt Roth - experienced 3-4 OLB, stout, lacks speed
Mathias Kiwanuka - experienced DE/OLB, local product, good size, injured
Mark Anderson - good size, speed, limited productivity
Disruptive pass rusher options:
Charles Johnson - extremely effective edge rusher, young (24) better in 4-3, very stout, would be third down pass rusher, could set edge, upside
Jason Babin - experienced, burst, quick/agile, 30 years, not used in coverage
Ray Edwards - experienced, perfect size, good rusher, lacks speed