Alan Bryant , Sep 18, 2009; 07:31 p.m.
I have used some old Tamron Adaptall-2 lenses with Canon EOS. They work fine. The most annoying thing is the fact that the apertures are not automatic, so if you want to shoot at f/8 you set the lens at f/8 and the viewfinder gets very dark. You'll have to meter the scene with the lens stopped down. Which is why it's called "stop down metering". You can do it in full manual mode or aperture priority mode.
If you can live with that, there are lots of lenses available at steep discounts. I don't know of any well-known manufacturer of mount converters, but "no brand" converters are available on eBay and sometimes in stores, and are usually not very expensive.