Best places to start
- Postmodern visual art overview → clearly describes how Postmodern art is a reaction to Modernism
- Wikipedia entry on Contemporary Art
- About Contemporary Art, a Getty Museum Education resource
- A great overview of Postmodernism from Tate museum (England)
- Wikipedia entry on Postmodern art → see especially 'Defining Postmodern Art' and 'Movements in Postmodern Art'
- Smithsonian article about attempting to define the difference between 'modern' and 'postmodern'