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
Air compressors can be expensive, but I think you'd be shocked to find out how many of your neighbors have one sitting idle in their garage. We always recommend that you borrow an air compressor to get started. If you're serious about making snow, here are a few options you can buy at a reasonable price. Renting from places like Home Depot is also an affordable option if you only are going to make snow a time or two each year.