BradTank

I actually like Harbor Freight for air tools. For a weekend warrior DIY-er, you don't need to spend a lot of money, and I've had really good luck with their stuff. They have retail stores everywhere, and although they're not really "commercial grade" tools, you'd be amazed how many mechanics use their tools at work.

You could probably get everything you need for around $250:

Basic Compressor
http://www.harborfreight.com/25-hors...sor-67847.html

Impact Wrench
http://www.harborfreight.com/air-too...nch-94803.html

Air Ratchet
http://www.harborfreight.com/3-8-eig...het-47214.html

They also carry all sorts of the additional accessories like air hose and fittings.

You don't really "need" air tools for 99% of the work on your car, but it definitely makes jobs go a lot quicker, and I use my air compressor for all sorts of jobs around the house.