Here's the official statement from the Chicago Bears website. Over at Windy City Gridiron, Dane Noble said that DT Tommie Harris's "late-season surge" wasn't enough to prevent his release. He's certain to catch on with another team, but at a much lower salary. While he wasn't part of their future, his release leaves them looking for a replacement.
OL Kevin Shaffer has been battling ineffectiveness for a while. In his two seasons with the Bears, he'd only started seven games for an offensive line that could have sure used the help. LB Hunter Hillenmeyer was originally drafted by the Packers, but he's been battling injuries for the past couple seasons. He only played in one game in 2010, and while he used to be a solid contributor, I expect his NFL career is over.
These three players were not part of their plans in 2011. While they have some depth at linebacker, they'll have to do something this offseason to add depth and improve their offensive and defensive lines.