From Yahoo.com:
12. Oakland Raiders
• Decrease in attendance: 21.32 percent
• 2001 W-L record: 10-6 (finished 1st in AFC West)
• 2010 W-L record: 8-8 (finished 3rd in AFC West)
• League championships last decade: none
More on the Raiders’ decline
11. Columbus Blue Jackets
• Decrease in attendance: 21.76 percent
• 2001 W-L record: 28–39–9–6 (finished 5th in Central Division)
• 2010 W-L record: 32-35-15 (finished 5th in Central Division)
• League championships last decade: none
More on the Blue Jackets’ decline
10. Indiana Pacers
• Decrease in attendance: 24.32 percent
• 2001 W-L record: 41-41 (finished 8th in Eastern Conference)
• 2010 W-L record: 32-50 (finished 10th in Eastern Conference)
• League championships last decade: none
More on the Pacers’ decline
9. Tampa Bay Buccaneers
• Decrease in attendance: 24.78 percent
• 2001 W-L record: 9-7 (finished 3rd in NFC Central Division)
• 2010 W-L record: 10-6 (finished 3rd in NFC South Division)
• League championships last decade: won Super Bowl XXXVII in 2002
More on the Bucs’ decline
8. Philadelphia 76ers
• Decrease in attendance: 24.94 percent
• 2001 W-L record: 56-26 (finished 1st in the Eastern Conference)
• 2010 W-L record: 27-55 (finished 13th in the Eastern Conference)
• League championships last decade: none
More on the 76ers’ decline
7. Arizona Diamondbacks
• Decrease in attendance: 25.05 percent
• 92-70 (finished 1st in NL West)
• 2010 W-L record: 65-97 (finished 5th in NL West)
• League championships last decade: won World Series in 2001
More on the Diamondbacks’ decline
6. Detroit Lions
• Decrease in attendance: 25.18 percent
• 2001 W-L record: 2-14 (finished 5th in NFC Central Division)
• 2010 W-L record: 6-10 (finished 3rd in NFC North Division)
• League championships last decade: none
More on the Lions’ decline
5. Oakland Athletics
• Decrease in attendance: 33.51 percent
• 2001 W-L record: 102-60 (finished 2nd in AL West)
• 2010 W-L record: 81-81 (finished 2nd in AL West)
• League championships last decade: none
More on the A’s decline
4. Pittsburgh Pirates
• Decrease in attendance: 33.78 percent
• 2001 W-L record: 62-100 (finished 6th in NL Central)
• 2010 W-L record: 57-105 (finished 6th in NL Central)
• League championships last decade: none
More on the Pirates’ decline
3. Seattle Mariners
• Decrease in attendance: 40.54 percent
• 2001 W-L record: 116-46 (finished 1st in AL West)
• 2010 W-L record: 61-101 (finished 4th in AL West)
• League championships last decade: none
More on the Mariners’ decline
2. Baltimore Orioles
• Decrease in attendance: 44.00 percent
• 2001 W-L record: 63-98 (finished 4th in AL East)
• 2010 W-L record: 66-96 (finished 5th in AL East)
• League championships last decade: none
More on the Orioles’ decline
1. Cleveland Indians
• Decrease in attendance: 56.08 percent
• 2000 W-L record: 91-71 (finished 1st in AL Central)
• 2010 W-L record: 69-93 (finished 4th in AL Central)
• League championships last decade: none
More on the Indians’ decline