I live just outside of Philadelphia and was listening to PHL departure tonight (via the LiveATC app on my iPad). Immediately after departure, US 754 (PHL-CDG), an A330-200, requested to enter holding in order to burn down fuel to their max landing weight for an emergency return.
They're still holding south of the field as of 8:05 EST. I didn't catch the nature of their problem. But based on the calmness of the radio transmissions, it doesn't sound like it's too serious. I'll keep listening and will update as anything else comes up.
[Edited 2013-05-07 17:08:38]