query_posts.php

<?php

query_posts( array( 
  'post_type'  => 'event',        // only query events
  'meta_key'    => 'event_date',  // load up the event_date meta
  'orderby'     => 'meta_value',  // sort by the event_date
  'order'       => 'asc',         // ascending, so earlier events first
  'meta_query'  => array(         // restrict posts based on meta values
                      'key'     => 'event_date',  // which meta to query
                      'value'   => array('2011-01-01','2011-02-01'),  // value for comparison
                      'compare' => 'BETWEEN',          // method of comparison
                      'type'    => 'DATE'         // datatype, we don't want to compare the string values
    ) // end meta_query array
  ) // end array
); // close query_posts call