My most recent creak sounded like it came from the BB. It only occurred while out of the saddle, so I new it was not related to the seatpost or saddle. To rule out the crank I applied some light oil to the chainring mounting areas and made sure all the bolt were tight.

Turned out to be the rear wheel at the skewers. The skewers were fairly new and I either didn't tighten them enough, or they just seated in and loosened a bit after a couple hundred miles. To be safe, I applied some light oil in the area and tightened the rear skewer. No more creak.