I say "jeez oh petes" a lot, but I don't know how widespread that is.
"Jeez oh pete, that's terrible!"
"Jeez oh pete, I can't believe it's 11:00 already!"
Also, "sucks" is very widespread in the US. Not really grandmother-appropriate, but not majorly offensive.
"You failed your math test? Man, that really sucks!"
"Working on Friday night sucks!"
My history teacher says "Joseph, Murphy, Maude!", but again, I don't think it's very widespread. ("Joseph Murphy Maude, what am I going to DO with you people?)
Also, "For the love of Pete!" ("For the love of Pete! My TV still doesn't work!")
I don't know if anyone has mentioned "heck" yet, as a substitute for hell ("What the heck? I know I put my keys here...)
You'd be safe with gosh, darn, or heck pretty much anywhere in the states. You can also say fricking, but that might be pushing it, in very conservative circles.