Thanks everyone for the nice words. I'll try to comment on some of the questions asked.
Most of the time players don't worry about flash, it's a part of the game.
In getting passes, you can contact the Athletic Director of the local high school and ask for a pass. You might have to trade off pictures for passes. Or, bluff your way onto the field, just act like you know what you are doing. Tell them you are from the yearbook company
ISO's - You might want to shoot at ISO 1600 and set your camera on manual at 250th at f4.0. It really depends on the field lighting conditions. You might want to get there early to do some test shots and adjust as the game progresses into darkness. The 40D isn't waterproof like the higher EOS pro models, so wrap you camera in a white garbage bag and cover the lens as well.
Well lite fields...........try shooting at ISO 1000, 1250 0r 1600. try some the advice above. the 105mm is a great lens, but not so great for sports action. Be careful and wait for the action to come to you instead of shooting plays 30 - 40 yards down the field. You might want to concentrate on the players along slidelines as the offense and defense comes off their.......focus on their emotions as are important and tell as story as well.