There are three main types: pintle, ball, and disc. I googled "fuel injector ball disc pintle" and came up with a few decent matches:
From our 3000GT DSM brethren -
http://www.stealth316.com/2-injectortypes.htm
Lots of pictures -
http://www.sdsefi.com/injectors.htm
Magazine article -
http://www.popularhotrodding.com/tec...PHR_Injection/
I think we have a pintle style stock injector, and I assume that's because it's cheapest. Most of the things I've found favor ball and disc because of better spray pattern and reaction time.