Twitter! Twitter! Twitter!
This made me laugh as it's so true...
It took me a little while to understand what Twitter was all about, and all though I'm not as mad on Twitter as @FrankArr or the other guys in his team, it's really useful for events and meeting people.
Although this Digg article makes an interesting read about Pownce vs Twitter. Is Pownce the next social networking service? And for how long?!