I may have mentioned this elsewhere already, but it's worth repeating: the Toronto public library system has passes for pretty well every museum in the city, usually given out every Saturday morning. The popular/expensive museums (Science Centre, ROM, AGO) go pretty fast, so you need to show up early for them (my TO neighbourhood is smart/poor, so people sometimes line up for an hour or two before the library opens on Saturday!). But other cool small museums (textile, ceramic, shoe) are often available all week long.