How to install this plugin
Install the plugin as usual, then click the edit link on the plugin page. Look for the line below in the code. Just delete the example links and add your own, dont forget to separate them with a comma.
// Array with sites to ping
$ping_arr = array("http://ping.example.com/", "http://ping2.example.com/");
The problem with this plugin is that it sends the ping before the site actually has been updated, well that sounds kinda stupid, but that was the only way I could have this to work. So if you are sending a ping to a site that reads your rss feed and then construct a link back to you, that link will point to your previously article.