According to Scout.com's Adam Caplan via his Twitter feed, the Cleveland Browns have signed former Bengals center Eric Ghiaciuc. Caplan's tweet states that Ghiaciuc will "back up Alex Mack." However, I would not guarantee that as meaning that Ghiaciuc will make the team -- after all, pretty much any center we sign would be a backup to Mack.
Ghiaciuc was originally selected by the Bengals in the fourth round of the 2005 draft. He certainly has some experience under his belt -- he started in 42 of the 48 games he played in with the Bengals from 2005-2008. Ghiaciuc spent some time off and on with the Chiefs and the Chargers last season but didn't see in-game action.
The Bengals weren't disappointed to see Ghiaciuc leave after the 2008 season. Over at Cincy Jungle, they believe that the change at the center position in 2009 improved their offensive line tremendously. In addition, for what its worth, Rotoworld states that "Ghiaciuc has been among the least effective offensive linemen in the league the past few seasons."