Obviously by now, everyone has heard of the successful test of the first proton beam at the LHC this morning.
As interesting as that, what's more fascinating to me is how the detectors are observing this beam. Since there's no collision yet, these detectors are not observing what they're designed to do, but they can still detect the beam pretty well. This link shows what the ATLAS detector saw this morning as the proton beam passed through it.
Edit: CORRECTIONS. I was just told that this is NOT from the proton beam passing through the detector. They have a beam stop right before the entrance to the detector, and what they detected were muons from the beam stop that were created when the high energy protons hit the beam stop.