http://www.seeedstudio.com/depot/female-shield-stacking-headers-6-pin-100pcs-pack-p-222.html
http://www.seeedstudio.com/depot/female-shield-stacking-headers-8-pin-100pcs-pack-p-223.html
Just got some of these from Eric, he had a manufacturer run these custom for Arduino shields. I put them on a homemade PCB I had around. Seems to be ideal...a little gap for the solder joint, not ridiculously tall like wire-wrap headers.