The answer to "what compressor?" is as varied as you can imagine. It all depends on your budget, your work space and whether or not noise is an issue.
I use a cheap 3 gallon pancake compressor, but it is LOUD. Mine lives outdoors and I run a line through the wall into my spray booth. Serves the neighbor right for letting his swimming pool pump run all night! Added bonus is it can fill up tires and run a small nailgun when needed. It works so well that when it dies (I have no illusions about cheap compressors!) I'll go and buy a larger tanked Sears unit to replace it.
Some use a small compressor or they might go for a unit such as the Smart Jet from Iwata, or go for an even more expensive unit like the Power Jet. Badger, Paasche, Silentaire and Sparmax all make excellent compressors.