There is an exhibit of 4x5 social documentary photography on display at the Royal Ontario Museum in Toronto, and it runs from 15 May to 11 Oct 2010.

"House Calls with my Camera" depicts the work of a physician who cares for frail house-bound seniors and documents their struggles:
http://www.rom.on.ca/exhibitions/special/housecalls.php

The ROM is Canada's largest and most visited museum.