Everyone here at RetroBlast is a big fan of Marvin Yagoda's famous "Marvin's Marvelous Mechanical Museum," an amazing collection of vintage coin-op oddities located up in Farmington Hills, MI. Marvin's got a fantastic and eclectic collection of strange games, and his site even hosts the invaluable Online Pinball Repair Guides that I've personally used several times to troubleshoot my pinball machines.