There's the Livestrong Challenge Philadelphia in August. I've done this ride 5 times. It's a great ride in a beautiful (hilly) area.
http://www.livestrong.org/Take-Actio...allenge-Philly
There's this ride in Gettysburg, which is also a beautiful place to ride:
http://worldteamsports.org/events/fa...-america-2013/
Search online for Tour de Cure and Bike MS -- they probably have rides in your area.
Also try asking at your LBS. And local cycling clubs might have information about local charity rides. One of the clubs I belong to posts a schedule of cycling events every year, which includes charity rides as well as club centuries and other events in the area.