The teams I have heard that are actual possibilities so far are the following: Bengals, Rams and Patriots.
Brooks really slowed down last year, but, then again, he was playing with a pulled hamstring. The problem with Brooks is his pride. Brooks always said that if he felt he could not play at the level he sets for himself...he would step aside. Problem is, Brooks never saw his play declining. It got to the point, where a number of people started to realize that the organization was going to have to make the decision for him.
However, I still think Derrick Brooks can play in the NFL and he could help strengthen a linebacker unit. Brooks would be a very valuable addition to a younger team that is on the verge of competing. His leadership would be worth his salary alone. He would show a young team how to prepare, how to work, how to conduct yourself with the media, how to represent the community, proper film study, etc.
If Brooks landed in New England, it would be for the chance to make a run at another title. He wouldn't have to be a leader there. He could simply go in, get his work done and help the Patriots try and earn their fourth ring.