Flatland Mfg builds some awesome rails that are perfect for a backyard setup.
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 @ 90psi or 5cfm @ 40psi.
This compressor has been used by dozens, if not hundreds, of home snowmaking enthusiasts all over the country (I own two). They work hard, run great, and at $119 (or less, they are frequently on sale) the price is nearly impossible to beat.
2 HP, 8 Gallon, 125 PSI Portable Air Compressor
A solid, portable compressor with a great price tag. A little bit heaver than the compressor above, but it is a higher quality unit and is oil-lubed (best option for long, snowmaking runs).
2 HP Electric Hand Carry 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