Food not Bombs:
http://www.foodnotbombs.net/

The People's Potato:
http://peoplespotato.blogspot.com/

Dumpster diving map (slightly out of date, but still a good resource):
http://maps.google.ca/maps?hl=en&tab=wl

An article on eating for free in Montreal (old but informative):
www.montrealmirror.com/ARCHIVES/2001/092001/cover.html