Going Back to 04:
Oregon State (Several Times)
SMU
Oklahoma (!)
Utah (Several Times)
Southern Miss (Several Times)
Oregon (Several Times)
TCU (Several Times)
Virginia Tech
Hawaii
Nevada
Fresno St
Not top quality, but some good teams. Plus, what would a team like USC, Florida, or OSU gain from playing Boise St? If they win, it's not a huge gain for them, but if they lose, they take a major knock. Boise has a difficult time scheduling respectable opponents.