Ping-o-Matic!: "Pinging lets dozens of services know you've updated your site and increases traffic to your blog. There are a number of services designed specifically for tracking and connecting blogs. However it would be expensive for all the services to crawl all the blogs in the world all the time. By sending a small ping to each service you let them know you’ve updated so they can come check you out. They get the freshest data possible, you don’t get a thousand robots spidering your site all the time. Everybody wins."

Looks like these folks hit a few more places with their pings than the folks at pingmyblog too, IceRocket being the most obvious one....