You get a "Logic" MOSFET. These turn completely ON at 5V. Look at the spec sheet for Vgs(on) being 5V or less. here is a typical example: http://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf
You get a "Logic" MOSFET. These turn completely ON at 5V. Look at the spec sheet for Vgs(on) being 5V or less. here is a typical example: http://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf