Where was 'Mamma Mia' filmed?

Mostly on the Greek islands of Skophelos and Skafos, although lots in Pinewood studiOS where they built replicas of the Greek island locations. This was so they could control the environment better for the big musical numbers, and was, in my opinion, handled badly.
The filming locations for Mamma Mia! (2008) were AgiOS Ioannis Chapel, Skopelos, Greece (wedding procession scene), Albert R. Broccoli 007 Stage, Pinewood StudiOS, Iver Heath, Buckinghamshire, England, UK, Damouchari, Pelion, Greece, Djemaa el Fna, Marrakech, Morocco, Greece, Kastani Beach, Skopelos, Greece, Laguna Beach, California, USA (beach scenes), London, England, UK, Pinewood StudiOS, Iver Heath, Buckinghamshire, England, UK, Skiathos, Greece, and Skopelos, Greece.