Add the following code to your functions.php
<?php
// original content display
// the_content('<p>Read the rest of this page »');
// split content into array
$content = split_content();
// output first content sections in column1
echo '<div id="column1">', $content[0], '</div>';
// output remaining content sections in column2
echo '<div id="column2">', implode(array_shift($content)), '</div>';
?>