I have software that searches Craigs list forabout 300 miles around me. I've found some really good deals over the years, 24-70mm L for $600, 35-350mm L for $500, 28mm f/2.8 for $15, 70-200mm f/2.8 IS for $800, 35mm L for $800, 135mm L for $600, and lots more. I am just patient, and move quickly when someone offers a deal. The lenses were all in excellent condition and had no problems. I also couldn't resist a Nikkor 300mm f/2.8 IF for $1100. It was a bit rough, and cost me $700 to tune up, but had no major issues.
I played with it on my 5D MII and on a Nikon D40X as well, since it had electronic focus, it would AF on even a low end Nikon DSLR.