I go to many museums and art galleries when I travel, including/especially to the ROM and AGO in Toronto. Both museums sell "advanced" memberships that offer reciprocal privileges (i.e., you get in free to hundreds of other museums that belong to their networks). But (a) they cost between $189 and $300 a year and (b) they exclude other Toronto museums (i.e., the ROM won't let you in free with an AGO membership).
So, while in Buffalo the other day, we bought an associate-level membership in the Albright-Knox art gallery, for $150. It gives me and the people with me admission to both the ROM and the AGO, plus all those hundreds of other museums (basically anything in North America with the words "contemporary" or "modern" in the name). One trip with an accompanying adult and student to the ROM ($46-$75) and the AGO ($49 up), plus the visit to the Albright-Knox itself, which is a pretty good gallery ($36), and it's pretty well paid for itself! And now I and friend(s) get in free to at least one museum in every city I visit for the next year.
So the trick is, (a) find museums that participate in reciprocal arrangements with museums you like, and (b) become a member (at the right level) of the cheapest one. It might not be in your home town, and it very likely won't be Canadian...