I'll do yooper's work for him. Notable free agents siginings and trades for Super Bowl winning teams.
New Orleans Saints 2009Jonathan Vilma via trade, gave up a 4th rounder (2008)
Jeremy Shockey via trade, gave up 2nd & 5th round picks (2008)
Bobby McCray (2008)
Jabari Greer (2009)
Darren Sharper (2009)
Pittsburgh Steelers (2008)Believe it or not: 0 notable acquisitions in the two previous years. Straight up build through draft
New York Giants (2007)Kawika Mitchell (2007)
That's as far as my personal notebook on NFL team's offseason's go.
The Saints were the only team of the last three champs who significantly improved their team through offseason means.
Fun fact: every member of the 2007 Giants draft class was active in their Super Bowl win, except for Adam Koets, who is still in their roster as a backup center.