Don't overlook the suggestion to use a fine tooth carbide tipped wood blade on a chop saw. They work really well to cut aluminum. If you already have a chop (miter) saw and a carbide blade, give it a shot, you'll be amazed at how well it cuts. I've also ripped 3/8" aluminum plate on my table saw with excellent results. The chips are hot, so wear some goggles and gloves. The good thing about using a miter saw is you can get some really accurate miters for welding up frames out of aluminum etc...