Here are the players that I've found to have won a major national college football award in more than 1 season. Note that players winning multiple awards, but all in the same season, are not listed here.
Players winning a National Award in 3 different seasons (it's a short list):
James Laurinaitis, tOSU - '06 Nagurski, '07 Butkus, '08 Lott
Players winning a National Award in 2 different seasons:
Glenn Davis, Army - '44 Maxwell. '46 Heisman
Doak Walker, SMU - '47 Maxwell, '48 Heisman
John Lattner, ND - '52 Maxwell, '53 Maxwell, '53 Heisman
O.J. Simpson, USC - '67 Walter Camp, '68 Walter Camp, '68 Maxwell, '68 Heisman
Archie Griffin, tOSU - '74 Walter Camp, '74 Heisman, '75 Walter Camp, '75 Maxwell, '75 Heisman
Dave Rimington, Nebraska - '81 Outland, '82 Outland, '82 Lombardi
Brian Bosworth, Oklahoma - '85 Butkus, '86 Butkus
Orlando Pace, tOSU - '95 Lombardi, '96 Lombardi, '96 Outland
Pat Fitzgerald, NW'ern - '95 Bednarik, '95 Nagurski, '96 Bednarik, '96 Nagurski
Danny Wuerfful, Fla - '95 O'Brien, '96 O'Brien, '96 Maxwell, '96 Heisman
Ricky Williams, Texas - '97 Doak, '98 Doak, '98 Walter Camp, '98 Maxwell, '98 Heisman
Sebastian Janikowski, FSU - '98 Groza, '99 Groza
Jason White, OKlahoma - '03 O'Brien, '03 Heisman, '04 O'Brien, '04 Unitas, '04 Maxwell
David Pollock, Georgia - '03 Hendricks, '04 Hendricks, '04 Bednarik, '04 Lombardi
Matt Leinart, USC - '04 Walter Camp, '04 Heisman, '05 Unitas
Daniel Supulveda, Baylor - '04 Ray Guy, '06 Ray Guy
Paul Posluszny, Penn St - '05 Butkus, '05 Bednarik, '06 Bednarik
Darren McFadden, Arkansas - '06 Doak, '07 Doak, '07 Walter Camp
Michael Crabtree, Texas Tech - '07 Biletnikoff, '08 Biletnikoff
Tim Tebow, Fla - '07 O'Brien, '07 Heisman, '07 Maxwell, '08 Wuerfful, '08 Maxwell
Players winning a National Award in 3 different seasons (it's a short list):
James Laurinaitis, tOSU - '06 Nagurski, '07 Butkus, '08 Lott
Players winning a National Award in 2 different seasons:
Glenn Davis, Army - '44 Maxwell. '46 Heisman
Doak Walker, SMU - '47 Maxwell, '48 Heisman
John Lattner, ND - '52 Maxwell, '53 Maxwell, '53 Heisman
O.J. Simpson, USC - '67 Walter Camp, '68 Walter Camp, '68 Maxwell, '68 Heisman
Archie Griffin, tOSU - '74 Walter Camp, '74 Heisman, '75 Walter Camp, '75 Maxwell, '75 Heisman
Dave Rimington, Nebraska - '81 Outland, '82 Outland, '82 Lombardi
Brian Bosworth, Oklahoma - '85 Butkus, '86 Butkus
Orlando Pace, tOSU - '95 Lombardi, '96 Lombardi, '96 Outland
Pat Fitzgerald, NW'ern - '95 Bednarik, '95 Nagurski, '96 Bednarik, '96 Nagurski
Danny Wuerfful, Fla - '95 O'Brien, '96 O'Brien, '96 Maxwell, '96 Heisman
Ricky Williams, Texas - '97 Doak, '98 Doak, '98 Walter Camp, '98 Maxwell, '98 Heisman
Sebastian Janikowski, FSU - '98 Groza, '99 Groza
Jason White, OKlahoma - '03 O'Brien, '03 Heisman, '04 O'Brien, '04 Unitas, '04 Maxwell
David Pollock, Georgia - '03 Hendricks, '04 Hendricks, '04 Bednarik, '04 Lombardi
Matt Leinart, USC - '04 Walter Camp, '04 Heisman, '05 Unitas
Daniel Supulveda, Baylor - '04 Ray Guy, '06 Ray Guy
Paul Posluszny, Penn St - '05 Butkus, '05 Bednarik, '06 Bednarik
Darren McFadden, Arkansas - '06 Doak, '07 Doak, '07 Walter Camp
Michael Crabtree, Texas Tech - '07 Biletnikoff, '08 Biletnikoff
Tim Tebow, Fla - '07 O'Brien, '07 Heisman, '07 Maxwell, '08 Wuerfful, '08 Maxwell