2007 - Detroit Red Wings defeated the Pittsburgh Penguins in the Stanley Cup
2008 - Pittsburgh Penguins defeated the Detroit Red Wings the following season in the Stanley Cup.
2008 - Boston Celtics defeated the LA Lakers in the NBA Championship
2010 - LA Lakers defeated the Celtics in the NBA Championship.
1975 - Pittsburgh Steelers defeat the Dallas Cowboys to win Superbowl X
1979 - Pittsburgh Steelers defeat the Dallas Cowboys again to win Superbowl XIII
1996 - Dallas Cowboys defeat Pittsburgh Steelers in 3rd meeting to win Superbowl XXX
1992 & 1993 - Dallas Cowboys defeat the Buffalo Bills in both Superbowls (XXVII & XXVIII)
Any other you guys know of feel free to add.