Pushed by unfolding events, a crop of "For Sale" signs has been popping up all over the country this summer; selling houses, boats, cars, motorcycles, RVs, and many other things. A lot of these signs are made from thin sheet steel or aluminum. One might inquire on Craigslist about possible used signs, or perhaps harvest directly from the sale or purchase of something. At the end of the last step, there are some other bowls I have made with this method, out of license plates and a stop sign. Pretty much any thin sheet metal will work.
The idea is to stress the metal up into a bowl shape without having to use any welding or complicated tools. By making a few slits here and holes there, you can bend, fold, and pin the metal together pretty quickly with some tin snips and a drill.
Assuming the sign is free, only a couple bucks' worth of fasteners are needed. Tin snips or a Dremel, pliers, a drill, a wrench, a screwdriver, and a ratchet would be handy to have close. Only takes an hour or two; most of the time is actually laying out the cuts more so than the actual construction.
It uses the same basic principles of this chair on a smaller scale: http://www.instructables.com/id/Nine_Square_Chair/
For sale here: http://www.etsy.com/view_listing.php?listing_id=28562050