[Beatnik]

OK I've noticed that its tougher to do pushups slowly than quickly. Does doing it more slowly make for a better workout?

[steveb]

Doing it slowly works you muscles.
Doing it quickly uses the springiness of your tendons. (less muscle use)

This goes for all exersizes. (curls, sit ups, etc.) You should always pause before moving again to get the max workout. You will fatigue faster, but that is OK if it is a better workout.

Note on push ups:
Alternate between elbows out and elbows at your side if you want more shoulder def.
Most people do not do eblows at your side style, but it will bulk your shoulders more.