Increasing the power output of the arduino pins

Does anyone here know how to increase how much current I can send to four 3.7v rotors via the arduino's digitalWrite() function, so I can put the to full speed?

Just have a look at the arduino's specs about max power (current) limits per pin AND in total per Arduino:

Link

If that is not enough, you have to put some transistors or equivalents in between the Ardu and your rotor(s).

Yes, have the Arduino control transistors for increased current flow. AOI510 or AOI514 work great with Arduino http://www.digikey.com/product-search/en?keywords=aoi514

JustAMan007: Does anyone here know how to increase how much current I can send to four 3.7v rotors via the arduino's digitalWrite() function, so I can put the to full speed?

"3.7V rotor"??? Can you rather less opaque and provide a link? Is this some sort of slotless motor? You know motors must never be driven directly from an Arduino pin, lest damage is done?