Great app note from Micrel on thermal management for voltage regulators.
This note discusses the LDO option, including choosing between simple three terminal regulators and full-featured five terminal regulators, and provides formulas, calculations, and a selection of commercial heat sinks for powering 3.3V logic circuitry requiring up to 5 amps from a standard +5V supply. Additionally, a “trick” for reducing heat sink requirements by distributing power dissipation with a series resistor is discussed.