Besides Cannes and Sun Dance, which fests usually produce award winning films?

You mean which fests have Academy Award accredidation? Around 40 festivals. You may be able to get a list from the Academy.

The ITOOFC (http://indietalk.com/showthread.php?t=4661) has plenty of awards. http://www.stevenrichards.com/images/smiley_fatcat.gif

(Not sure if the Academy recognises them yet, though) http://www.stevenrichards.com/images/smiley_ninja.gif

I guess I meant to say the fests that have a reputation of showing films that end up winning the oscars. Films like American beauty, Monster, etc.

About 40 festivals have Academy accredidation, which means if it wins an award, it is sent to the Academy for consideration for a nomination. Yes, Sundance is one of them.