Your air compressor needs to be able to pump enough enough to turn water into snow. Look for the CFM (flow: cubic feet per minute) and PSI (pressure: pounds per square inch) ratings on any air compressor to see if they'll work. The minimum you'll need is about 4-5cfm @ 40psi.
This style of compressor has been used by dozens, if not hundreds, of home snowmaking enthusiasts all over the country. They work hard, run great, and at around $200 (or less, they are frequently on sale) the price is pretty reasonable.
3.5 HP, 10 Gallon, Portable Air Compressor
Slightly less volume than the first option, this compressor is built with a little higher quality and slightly better overall design.
If you want your compressor to last a bit longer, this might be a good option.
1.3 HP, 8 Gallon, Portable Air Compressor
This is a solid, heavy duty compressor that can not only crank out plenty of air, it can do so quieter and longer than most compressors out there. Still not the high-end contractor grade, but a good choice for the serious snowmaker.
Campbell Hausfeld VS5006 15 Amp 2 Horsepower 20 Gallon Oiled