Ping services allow you to automatically notify sites like blog directories and search engines that your blog has been updated. Whenever you make a new post, Wordpress will try to ping all these websites one by one and that process will waste a lot of time before you can make another post or do anything in Wordpress. In order to avoid this, you should use a plugin for Wordpress called No Ping Wait. This plugin actually puts the process of pinging in the backlog and allows you to continue working seamlessly by removing any kind of delays. Download this plugin, install and activate it on your Wordpress blog.
The bigger your ping list the higher the chances of receiving traffic from those sources, so check out the list below and include it on your blog (Wordpress users can modify their ping list on the Control Panel, then Options, then Writing).