PHP-eSeller is a PHP/mySQL application for selling mp3 and other digital files from your web site.
PHP-eSeller will work with Google Checkout and with PayPal. As PHP-eSeller is based around IPN (instant payment notification) it will work with all PayPal accounts.
For a full description of PHP-eSeller, go to http://www.withinweb.com/phpeseller/index.php