my bike was creaking last week, driving me nuts, i had just bought a new bottom bracket cuz it had cermaic bearings and was on closeout for $30. i was planning to wait til next year to install it but then i heard the creaking. i put the new bb in, still creaking. take it to my bike shope, he steps on the crank from the side to try to reproduce the creak. he does, he immediately goes to the rear wheel, flips open the quick release, makes an adjustment and flips it closed so it's facing a different way from how I had it and the creak was gone!!!
I felt like a dumbass, i had just gotten a titanium lightweight skewer set also on clearance and apparently i tightened it too much or something but the moral of the story is sometimes its not a major issue at all, just a stupid little issue!