Some great hackers over at ALLDROID has successfully overclocked the Moto Droid to 1.1GHZ. Yes ladies and gentlemen 1.1GHZ. Although running the phone at 1.1GHZ is unstable it runs perfectly fine at 800MHZ which is 200MHZ over the 600MHZ that the processor has been rated at. In fact ALLDROID has it running stable at this speed.
All you need to do to get started is have a root ed Droid, then head over to ALLDROID for instructions on how to get your phone overclocked. Be warned that pushing the phone over its recommend limit will shorten the life span of your phone and it could break it as soon as you do it so proceed at your own risk.