Originally Posted by Brian Sorrell
However, creaks are notoriously hard to find -- it could even be your seat post -- I had this problem and I almost lost my mind trying to find the source of the creak. My most recent creaking sound was the rear derailleur cable housing rubbing against a cable stop -- I swore it was something in the bars -- took a week to find it by trial and error. Invest in a bit of bike grease and you can eliminate lots of annoying sounds.
You are so right! I once spent an entire afternoon trying to find a creaking noise on the bike. It finally turned out that it wasn't even the bike, just a clip I was using to hold my keys on my belt.
(Of course I doubt if this is the OP's problem.)