If you are familiar with Twitter, then consider Pownce another step in that direction. Pownce lets you send links, files, etc. to your friends, and the public if you wish. The system is very similar to what Twitter does, but it does seem a little bit more polished. It's pretty simple in what it does, and it seems to work quite well as I have no ran into any problems so far. The interface is simple and clean, and it's slightly customizable as you can choose from a few themes.
Right now there seems to be quite a buzz about Pownce, and right now it's invite only, and it seems people are even selling the invites on eBay for a few dollars. I have one invite left, so if you are really interested in trying out Pownce leave a message here and I will give one away.
