The most common place (by far) for spokes to break is right at the elbow. That's usually due to inadequate tensioning.

Another common place for spokes to break is where they enter the nipple. I solved that problem on a Bike Friday triple by relaceing the rear wheel 2 cross rather than 3 cross.

The only other place where I've seen a spoke break has been due to overshifting the chain and buggering the spokes.