Since you have already established you like to visit museums, perhaps you should join your favorite museums, and with a little care, you can make a membership go further. To that by spend a bit more to support the museum of your choice at the level to get membership in a reciprocal program. This will get you free or reduced membership in other museums around the country (and for some, the world)
One of the most common ones is North American Reciprocal Museum (NARM) Program – the list of member museums is at: https://narmassociation.org/
For art lovers, at many major art museums, check out: Art Museum Reciprocal Network(s), unfortunately this is more a title than a specific program. check various museums to see how it might vary. This usually is included in memberships over $150/year.
Here is a paper (from 2014) describing some of these programs: Reciprocal_Membership_Programs.pdf.
Here is a map of a common set of such offering: Map of an AMRN
Here are others:
For college and University museums, look for “College and University Reciprocal Membership Program”, again a title not a specific program.
In general, an regular museum goer should see what Reciprocal offerings might be useful for their next year of travels. Be warned many have special restrictions, a common one is limited reciprocal privileges for museums closer then 50 miles from the granting museum.
For Science and Technology Centers, (ok fancy word for Museums) check out the ASTC Travel passport program, more at http://www.astc.org/members/passlist_about.htm and you can search or find a downloadable reference list at: http://www.astc.org/members/passlist.htm
American Horticultural Society reciprocal program (RAP) includes admission to more than 220 gardens, conservatories and arboreta in the United States, Canada, Virgin Islands and West Indies.
RAP-pdf or Click here for listings.
Free for a day, Smithsonian Magazine museum day live! See details and download your free ticket http://www.smithsonianmag.com/museumday/
The International Council of Museums (ICOM) established International Museum Day in 1977 to encourage public awareness of the role of museums in the development of society.
From America to Oceania, through Europe, Asia and Africa, International Museum Day is a special moment for the museum community. On this day, participating museums interpret an issue that concerns all cultural organisations. International Museum Day is also a fantastic opportunity for museum professionals to meet their public. At the heart of society, museums are institutions dedicated to its development.
Traditionally, International Museum Day is organised around 18 May. It can last a day, a weekend or a whole week, the objective being to meet at the museum with the motto: “Museums are an important means of cultural exchange, enrichment of cultures and development of mutual understanding, cooperation and peace among peoples”.
Each year, IMD gathers more museums from all around the world. In 2012, 32,000 museums from 129 countries on five continents participated in the event. http://network.icom.museum/international-museum-day