I spotted an ad on Craigslist for Dibond and Alucobond, and wound up buying some.
He's got a lot of Alucobond in the 12" x 18" range, plus some larger sheets of Dibond.
If you've never worked with Alucobond or Dibond, it's wonderful stuff. It's a composite panel with a polyethylene core sandwiched between two thin aluminum facings, with a very tough and attractive finish, suitable for long term outdoor exposure. Easily cut with ordinary woodworking tools. Can be grooved and bent by hand, looks like solid aluminum if you do it right.
Great for signs, fixtures to display art, control panels, etc. Would make top notch reprap parts.
Email addy is wang at wang.me. He still has listings for "Dibond" and "Alucobond" on CL.
Anything left at the end of the week is probably going to Axeman.