On April 12th, I delivered the talk "Dialects of early Icelandic" in the series Málstofan on Channel 1 (Rás 1) of the National Brodcasting Service (RÚV). The Icelandic language has undergone great many changes throughout its history. These changes did not spread throughout the entire community in one fell swoop. Instead, their spread did in many instances take several centuries. Inevitably this lead to some dialectal differences.
You can listen to the talk on the Málstofa web (in Icelandic).