The MCNY is great. It's permanent exhibit on protests in NYC is really good. It starts with the Flushing Remonstrance up to protests on LGBT rights and beyond. MCNY has a huge photo archive that they use well here, especially for the LGBT Rights and Women's Suffrage movements.
This was a large collection of WWI posters, and they were in amazing condition, but that wasn't all there was to the exhibit. IT invluded some short ads and movies played to encourage support for the war and relief efforts.
This exhibit focused on fashion from the early 60's: Jackie Kennedy dominated this section, up through the early 70's. It wasn't just clothes, it also included jewelry and accessories.