This happens becuase your chainstays are short. Calfee (www.calfeedesign.com) makes his bikes with real long chainstays. My front wheel never pops a wheelie, not even on step, slow climbs, or during sprints. I've always had that same problem before I switched to Calfee. Most people think long chainstays mean a sluggish bike, but I don't find that to be true, and my two podium finishes on a Calfee in my last two crits would tend to support my beliefs!

Anyway, since you probably don't want to change frames, the other suggestions above are good ones, but I just thought I rant a bit about frame geometry, because that is the root cause. Also getting a bit lower may help, bars with a deeper drop.

Also if you can pedal toes down and set your pedals up so that you are more on the front of your foot, that could also help.