One ping (service) to rule them all: Ping-O-Matic

Ping-o-Matic is now not only a HTML form-based service that you can use to notify multiple sites of your new weblog entry. This weblog entry let us in on the new ping URL http://rpc.pingomatic.com/ that you can use to replace the long list of URLs you're currently pinging everytime you make a new weblog entry.

This means no more waiting for your weblog software (be it Movable Type, WordPress, or something else) as it pings multiple services.