Whether you already love Art Deco, or just want to get a taste of it, the Wolfsonian is a must-see while in Miami Beach. They have an impressive permanent collection of artifacts ranging from home furnishings to industrial design to graphic art. Traveling exhibitions round out the offering, bringing all sorts of interesting themes and topics. Whatever you pay to go through this gem of a museum is well worthwhile.
I particularly like the cafe and gift shop. Very cool items that you don't find just anywhere, and an excellent collection of books for the more serious student of the era.