Carolina's hosting various fringe offensive linemen, most notably Kevin Boothe, a journeyman last with the Giants. He's listed as profootballfocus's 7th best available guard - they note good run blocking, below average pass blocking, and a general positive in a lack of penalties. Boothe is talking to various teams, including returning to the Giants.
Other linemen include former undrafted Panther Frank Omiyale - who played LT for a few games here, then got snatched up in '09 by the Bears, and then finished last season as a Seahawk, and Chris Williams, an OT that went a pick after Jonathan Stewart in the 2008 draft (two other linemen went between there and Jeff Otah). Neither are currently starting quality.
Another former Panther, Geoff Schwartz, hit the market and didn't stay long; he's now a Chief.
Former Chargers Antonio Garay, Antoine Cason are off the market. Waiting for the market to dry out has consequences, and that includes losing out on these solid starters - they would've plugged two short term holes on a defense that has room to improve. But, that's part of waiting, and both were in enough demand to cost more if pursued.
Still, Carolina is pursuing options, which is progress.