Here is the list, in chronological order of the note worthy signings since 2000:
Joe Andruzzi 2000
Bobby Hamilton 2000
Otis smith 2000
Grant Williams 2000
Larry Izzo 2001
David Patten 2001
Roman Phifer 2001
Antowain Smith 2001
Mike Vrabel 2001
Ken Walter 2001
Christian Fauria 2002
Rosevelt Colvin 2003
Rodney Harrison 2003
Tyrone Poole 2003
Don Davis 2003
Russ Hochstein 2003
Josh Miller 2004
Keith Tralyor 2004
Doug Flutie 2005
Tim Dwight 2005
Reche Caldwell 2006
Jabar Gaffney 2006
Junior Seau 2006
Tory James 2007
Sammy Morris 2007
Donte Stallworth 2007
Adalius Thomas 2007
Kelley Washington 2007
Randy Moss 2008
#1 - Mike Vrabel
Came to the Pats before hitting his prime and has been reliable ever since. He has produced both on the offense and the defense, but hasn't been the leader with Bruschi holding down the fort.
#2 - Rodney Harrison
Personally, I think he had his best years before coming to the Pats. He has provided experience and leadership to the secondary and his absences proves his value to the secondary. Without him, the secondary seemed vunerable up until this year when he had to sit out the first four games. But he hasn't been healthy and his reliability isn't to the level of Vrabel.
#3 - Randy Moss
Would be first if we took into account last season, but last year he wasn't a free agent signing. Going into 2008, he has to be the biggest and best signing for what he will allow the offense to continue doing. If he only has half the production he did last year, he will hold down this spot.
Honorable mention:
Izzo - A mainstay on special teams.
Andruzzi - May not had been a pro-bowler, but he was solid on the line.
Bobby Hamilton/Keith Traylor - Both were useful in stopping the run and making the defense capable. Traylor wasn't around long, but he needed to replace Washington after he signed with Raiders.
Caldwell - Great in year he was around, but he had serious issues in the playoffs.
Gaffney - Was big in the 2006 playoffs and then last year.
