Endeavour was supposed to launch today, but "a leak associated with the hydrogen venting system" has delayed the flight until at least June 17. Hydrogen tends to blow up, so engineers are being cautious. This is a frequent occurrence with the Shuttle, so I'm not worried about accidents, but it is a bummer.
I'll note that June 17 is when the Lunar Reconnaissance Orbiter is due to launch, so one of them will have to be moved. NASA engineers meet on Sunday to figure that bit out, and NASA should announce plans shortly thereafter.
In cooler news, the commander of this mission, Mark Polansky, has a Twitter account! So those of you on Twitter can follow him when he gets a chance to tweet from space. I use Twitter to cover launches and space news as well, and I'll have more info there when I hear it.