If you are going to Stockholm you shouldn't miss the Fotografiska Museet which is just great! Nice mix of different photo exhibitions shown in a beautiful industrial building from the early 20th century, right at the docks of Stadsgården. At the moment, there is a Robert Mapplethorpe show - you might have heard of it. But don't miss Liu Bolin's The Invisible Man, which is on till September 11th. The 38 years old Bolin is a chinese artist who works with a sort of camourflage technique, putting himself into the photographies and becoming visible and invisible at the same time.
Fotografiska Stockholm, Liu Bolin Exhibition