I hate sites like pingomatic.com they are great if you are just starting or have something you just want to promote for fun but personally I use pingler.com because other wise I will only ping the site once and never again. Or pinglooza.com - Same service but alot cheaper.
PING is a computer network tool used to test whether a particular host is reachable across an IP network. If you are having connectivity problems, you can use the PING command to check the destination IP address you want to reach and record the results. The PING command displays whether the destination responded and how long it took to receive a reply. If there is an error in the delivery to the destination, the PING command displays an error message. If you want to know how a website gets pinging, Check this site:- Whoisxy.com. You can also use the PING command to: Ping your computer to determine that TCP/IP is functioning. Ping the local router to determine whether the router is running. Ping beyond your local router.