My hubby is assistant coach for the West MI JDRF Ride team. This year they will be training to ride 100 miles in Death Valley:
http://www.jdrfwestmichigan.com/
blog: http://jdrfwestmichiganride.blogspot.com/

We're also planning to do the Holland Hundred ride and the Colorburst Tour in October.

Velo City Cycles in Holland organizes a ton of group rides and the store owner is a really great guy. He is the head coach for the local JDRF Ride team chapter.