NASA's highly successful Discovery Program is allows the scientific community to propose and execute focused, scientific investigations that compliment NASA's larger planetary exploration.  Its goal is to launch numerous small missions with a faster development phase, each for considerably less than the cost of larger missions. The Discovery program has successfully completed many missions to date including voyages to the Moon, Mars, and Mercury, comets, and asteroids.  The author will present an overview of the missions to date, including those currently under development, and give an overview specifically of the Deep Impact Mission.