If you're looking for something to do in NYC this weekend, I recommend paying a visit to The International Vintage Poster Fair taking place through Sunday at the Metropolitan Pavilion, 123 W 18th St, 4th Floor. Admission is $15 for the whole weekend, and you'll get up close to some of the most beautiful vintage lithographs from around the world, all vetted for their authenticity.
A favorite of mine was the Ma Maison de Papier booth. The Belgian dealer was extremely knowledgeable about each poster, enthusiastically explaining the history of the products that were featured in the posters, cultural references that were humorous or dramatic at the time the poster was made, printing techniques, and the backgrounds of the illustrators.
Also of interest was The East is Red, posters from Mao's China. The images are very striking, and some quite affordable. If you liked Art and China's Revolution (through Jan. 11 at Asia Society), you'll want to loiter a bit at this booth.
I also saw an Alphonse Mucha being sold. Damn those losing lottery tickets! It could've been me...