What is there to tell? It says so right on the website: It allows you to update twitter/facebook/tumblr and a host of others (shown on the front page) with a single message. This means you don't have to log in and post the same message over and over again on each website.
Hey, thanks for this post. Never heard of ping.fm. I just checked it out and joined. Man what a time saver that will be.
Ping.fm takes care of updating status messages in all the social networks in one go. It supports more than 30 networks including all the popular networks like Twitter, Facebook, Flickr etc.