The NFL Lockout has not ended and likely won't for at least the next week or two. There has been no activity in the past 108 days, but once the new CBA is complete, there will be a flurry of activity.
While notable guys on offense like Peyton Manning are free agents, it is unlikely that the big names will change teams. Judging from years past, it is normally the defensive players that sign with a new team. This year's most sought after free agent player on defense is Nnamdi Asomugha. If he decides to leave Oakland, it could shake up this list.
Looking at the rosters as they are set right now, I am assuming that every free agent is going to re-sign with their previous team. Obviously that won't happen, but it is impossible to know which ones will leave and which ones will stay.
There are some great young defenses out there that came up just short of this list. Teams like Tampa Bay, Baltimore, Kansas City, and the New York Giants could all make the top ten, but this list is more exclusive.