Got intrigued with the discussion of sponsored football stadiums & found out the following: Of the 30 stadia for the NFL's 31 teams (the two NY teams share a home)
    17 are currently sold off and two sold naming rights to individual entrance gates - 63%
     4 are in the process of seeking new name-buying sponsors for current or new stadia - 13%
     6 seem to be unwilling or very unlikely to sell naming rights to corporations - 20%
     I am too dumb to calculate this out to 100%

The stadiums in order of newness are...

Cowboy Dallas - Cowboys Stadium - (waiting for naming sponsor)
Indy Colts - Lucas Oil Stadium - (corporate sponsored)
Arizona Cards - University of Phoenix Stadium - (corporate sponsored)
Philly Eagles - Lincoln Financial Field - (corporate sponsored)
Chicago Bears - Soldier Field - (despite 2003 renovation costs, no naming rights sold)
Houston Texans - Reliant Stadium - (corporate sponsored)
New England Pats - Gilette Stadium - (corporate sponsored)
Seattle Seahawks - Qwest Field - (corporate sponsored)
Detroit Lions - Ford Field - (corporate sponsored)
Denver Broncs - Invesco Field - (corporate sponsored)
Pittsburgh Steelers - Heinz Field - (corporate sponsored)
Cincinnati Bengals - Paul Brown Stadium - (Cincinnati decided against selling naming rights)
Cleveland Browns - Cleveland Browns Stadium - (Cleveland sold naming rights to its 4 entry gates instead - cha-ching!)
Tennessee Tight'ns - LP Field - (corporate sponsored)
Baltimore Ravens - M&T Bank Stadium - (corporate sponsored)
Tampa Bucks - Raymond James Stadium - (corporate sponsored)
Washington Redskins - FedExField {sic} - (corporate sponsored)
Carolina Panthers - Bank of America Stadium - (corporate sponsored)
Jacksonville Jags - Jacksonville Municipal Stadium - (corporate naming rights expired in '07)
St Louis Rams - Edward Jones Field - (corporate sponsored)
Atlanta Falcons - Georgia Dome - (government owned) (!)
Miami Dolphins - LandShark Stadium - (really dumb corporate sponsorship)
Minnesota Vikings - Hubert Humphrey Metrodome - (unnamed replacement stadium in the works)
New York Giants - Giants Stadium - (unnamed replacement stadium in the works)
New York Jets - Giants Stadium - (unnamed replacement stadium in the works)
New Orleans Stains - Louisiana Superdome - (owners currently not selling name rights)
Buffalo Bills - Ralph Wilson Stadium - (corporate naming rights expired in '98 & not resold)
San Diego Chargers - Qualcomm Stadium - (corporate sponsored)
Kansas City Chiefs - Arrowhead Stadium - (currently seeking naming rights sponsor)
Oakland Raiders - Alameda County Coliseum - (corporate naming rights expired in '08 ; new stadium probable)
San Fran 49ers - Candlestick Park - (corporate naming rights expired in '02)
Green Bay Packers - Lambeau Field - (Green Bay sold naming rights to its 5 entry gates instead)