I saw Posterous through the TweetDeck update and was pleasantly intrigued by the interface. Couldn't have a simpler concept for publishing personal stuff if you ask me, so I decided to give it a try and see what it looked like. I'm pretty impressed to be honest, driving content via email, sms, or any other number of input methods and having it appear automagically on a website somewhere with panache is a pretty cool idea.
Update: I've since dug into the Posterous interface and I've been even more impressed. It was easy to add a DNS record for www.davemo.com in EasyDNS and have it point to this site in a matter of minutes. Yay :)
Facebook connect integration, auto embedding of media including images, video, music and the ability to post via so many methods. This just makes blogging as easy as sending email.