zacster - There is a light mounted to the bars. Tightened it, and one brake pad, as well as a bottle cage. The last time this happened, now that I remember it, it turned out to be a bottle cage. I'll take it out tomorrow through a long descent; should be a good test.

FBinNY - pinch bolt on brake cable is really tight, but the cable end protrudes about two inches. I'll try putting a dampener on it if the noise persists. Good theory.