CarbonS2000

Ive got a Tamron AF 75-300mm f4-5.6 I got it for like $150. I wanted a cheap zoom to start playing with before I went with an L. I was wondering if anyone knew if the canon 1.4x or 2x extender would fit on the Tamron lens. I have a 30d body.

Heyitsgary

I doubt it. I have borrowed a few lenses for my Nikon, and none have worked with my TC. Even some of the Nikon lenses don't work with it.

I borrowed a friends Tokina 80-400 with a 2x Tokina converter - the openings on the lens side are different, they were not interchangable.

Poindexter

It will work, but with f4-5.6 it is going to make your maximum aperture much smaller. It will also give you a soft image on that lens.