Feedburner Pingshot

I use pingshot.  It's easy to activate, you get to choose the services that get pinged when you  post, and you don't have to do anything to activate it - you just post normally and pingshot does the rest.

If you are using Feedburner to burn RSS feeds for your blog, you can activate its Pingshot feature to ping web services automatically every time you update your blog. Feedburner Pingshot pings to 6 web services and you can add 5 more addresses to ping.