There are still plenty of free agents available who can significantly help this team. To name a few:
Thomas Jones - A superior between the tackle runner that the Pats haven't had since Dillon
Larry Foote - Solid ILB who is great against the run and good in coverage
Jason Taylor - A very good situational pass rusher
Derrick Mason - Older, but good route runner, versatile, style is a good fit for the Pats' offense
DeShea Townsend - Pats gave him a tender offer. Solid CB who could an one year placement at CB and potentially a FS for several years
LJ Smith - good receiving TE and decent blocker
Reggie Kelly - Very good blocking TE and a good short yardage receiver
Vonnie Holiday - Experience in the Pats' 3-4 in both Denver and Miami. Good pass rusher at DE. Would be an upgrade over Jarvis Green
Adewale Ogunleye - Might be a low risk, high reward experiment to convert to an OLB. He could have a McGinest like revival by taking his hand off the ground and moving outside the tackle. He greatest skills are to anticipate the snap well and having some speed. His problem is he can get overpowered rushing inside the tackle. Moving to OLB might actually allow him to exploit his strength and hide some of his weaknesses. Wasn't in love with the idea at first, but more research tells me he might be worth a risk if we can get him cheap.
Ryan Clark - A smart, physical, athletic FS. He can lay the wood (just ask Wes Welker) and he is tough. He is the type of player the Pats used to have at multiple positions on defense.
Chris Chambers - Not in love with the guy, but he is a big WR who can get down the field. Has talent to be a #2 or #3 on this team
Antonio Bryant - Elite talent with consistency issues.
Josh Reed - A good #3 or #4 WR option. Good route runner with good hands. More quick than fast. The type of WR the Pats usually had prior to Moss and Welker
LaDainian Tomlinson - Yeah, I know. Mr. Classy. Not a lead back anymore, but could excel in a Kevin Faulk type role.
And those are just the UFAs. Yeah, none of those guys are as flashy as Peppers or Boldin and many of them are only one or two year stop gaps. But if you can get 4-5 of these guys (very doable), you can significantly upgrade many of the team's weaknesses in multiple areas rather than spending a boatload to fix one area.
These are the type of moves that got the Pats to the Super Bowl in 2001 and to a certain extent in 2003 and 2004. In recent years, many of these types of players have not been available because the cap was such that players didn't release them. It is time for the Pats to go old school and pick up solid veterans who have been shedded from their roster because of salary issues over production issues.