I just signed up for resellerratings.com and decided it would be cool to put a link to have my site rated on checkout. It was a very very easy hack. I'll include my file so you can look, but basically I just changed this line of code:

includes/languages/english/checkout_success.php

Code:
define('TEXT_THANKS_FOR_SHOPPING', 'Thanks for shopping with us online!<br><br><a href="http://www.resellerratings.com/survey_popup.pl?seller_id=9241" onclick="window.open(\'http://www.resellerratings.com/survey_popup.pl?seller_id=9241\' ,\'ResellerRatingsSurvey\',\'width=625,height=400,scrollbars\'); return false;">Please take this survey and let us know what you think of our store.</a> ');
Resellerratings.com gives you the code. Basically just take my code and change the seller_id to your own. I didn't opt for the pop-up rating on every order as I've found sites that have that to be annoying. If I want to rate someone I'll rate them I figure.

Anywho, thought you guys might like that. Its cool, and its free. Does anyone have any notes on any ways I could improve this? Maybe use bizrate.com or one of the others?

Thanks