Patrick, I've actually only worked on just a few air compressors; my little sideline business is repairing/rebuilding automotive air tools; ratchets, impact wrenches, drills, sanders, saws, cut-off tools, shears, air hammers, etc.
As for which air compressor to buy; that's almost like asking which tractor to buy./w3tcompact/icons/laugh.gif Have to know what you intend to run off it, how much it'll be used, etc. Like I just responded to John Miller, those DeVilbiss oiless are cheap and work well, but for myself it's got to be a cast iron two cylinder compressor with oil in the crankcase. The horsepower ratings on electric compressors, for all practical purposes, mean nothing. You need to see what the specs are for pressure (most go about 120 psi, but the expensive ones go 175 and up), and what volume it moves (cfm). Almost all air tools are rated for a maximum of 90 psi, but a lot of garages run the 175; makes their air tools more powerful, and keeps me in business when they break them. When you look at the volume the compressor can handle, most impacts and ratchets don't use a lot, but sanders, paint guns, sandblasters, and air guns for cleaning things can require more than a lot of small compressors can keep up with. I used one like John pictured, doing some sandblasting; just had to stop every two or three minutes to let the compressor catch up.
As for brands, I'd even go so far as to say to buy a cheap one unless you intend to use it all day every day; things like DeVilbiss, Craftsman, Campbell Hausfeld; just get one of their cast iron compressors with oil in the crankcase. I'm using a 220 volt, cast iron V-twin, 60 gallon tank, Puma that was on sale for $600 about 3 years ago (plus the water separator and a few other accessories).
Bird