Thanks geomorph for all of the awesome pictures on this thread.
A few random museums I had pictures of that aren't on this thread yet:
Museum: Perot Museum of Nature and Science
Location: Dallas, Texas, USA
Architect: Thom Mayne / Morphosis Architects
Completed: 2012
Museum: Museo de Arte de Ponce
Location: Ponce, Puerto Rico, USA
Architect: Edward Durell Stone
Completed: 1965
Museum: Museo de las Americas
Location: San Juan, Puerto Rico, USA
Architect: ?
Completed: Ballajá Barracks 1864; museum opened 1992
Museum: Erie Canal Museum
Location: Syracuse, New York, USA
Architect: ?
Completed: weigh lock building 1850; museum 1962.
Museum: Museo Nacional de Antropología
Location: Mexico City, Mexico
Architect: Pedro Ramírez Vázquez, Jorge Campuzano and Rafael Mijares
Completed: 1964
Museum: Tokyo National Museum (Honkan building)
Location: Tokyo, Japan
Architect: Josiah Conder; redesigned by Watanabe Jin after 1923 earthquake
Completed: 1872; 1938
Museum: Osaka Takoyaki Museum
Location: Osaka, Japan
Architect: ?
Completed: ?
Museum: National Museum of Korea
Location: Seoul, South Korea
Architect: Chang-Il Kim of Junglim Architects
Completed: 2005
Museum: Museu Arqueológico do Carmo
Location: Lisbon, Portugal
Architect: ?
Completed: 1389-1423; partially destroyed by earthquake in 1755; museum opened 1864
Museum: Pena National Palace Museum
Location: Sintra, Portugal
Architect: ?
Completed: 1854; museum 1910
Museum: University of Alaska Museum of the North
Location: Fairbanks, Alaska, USA
Architect: Joan Soranno, GDM/HGA
Completed: 2005
Museum: National Museum of Cambodia
Location: Phnom Penh, Cambodia
Architect: ?
Completed: 1920