This was about 3 days ago. The California Near Space Project (CNSP) team launched 4 balloons. Two of them were short-duration, high-altitude flights. The other two were long-duration floaters (K6RPT-11 and K6RPT-12). First, the announcement:
Our goal is to reach neutral buoyancy at a very high altitude and fly as far across the United States as possible.
The balloon not only made it through north america. It completely crossed the Atlantic, entered Spain through Jerez de la Frontera and exited towards Italy. After a 57 hours flight, it eventually descended on the Mediterranean sea off the coast of Algeria.
Look at the green portion of the trajectory after the balloon passed New Jersey. These were quiet hours of uncertainty until the signal was picked up again from the Azores:
Launch time was 2011-12-12 00:40:31z. The last packet was heard on 2011-12-14 09:46:30z:
You can see the full trajectory on aprs.fi while it's recent:
Update: Below is a video of the launch: