Suburban Cyclists Unlimited (www.suburbancyclists.org) offers two of the best run rides around the Mid-Atlantic region.
(1) May 12, 2007, Quad County Metric. From scenic Green Lane Park, Green Lane, PA, ride 21, 31, 45, 53, 68, or 76 miles at your own pace on low-traffic back roads. The 21-mile route avoids the longest climb and is suitable for casual riders. The longer routes are on rolling to hilly terrain. The 53- and 76-mile routes include the 8-mile "Intensive Climbing Unit" extra- hilly segment with 1,200 ft additional climbing. A flat 10-mile ride on the unpaved Perkiomen Trail is also available.
(2) August 27, 2007, Lake Nockamixon Century. From Warrington, PA, ride 25, 50, 75, or 100 miles on rolling terrain with a few hills. A hilly 107-mile Intensive Climbing Unit century route is also being offered. All riders will visit picturesque Lake Galena in Peace Valley Park. 50-to-100-mile riders will also visit our well-stocked rest stop at scenic Lake Nockamixon.

And don't forget the classic Central Bucks Bike Club's Covered Bridges Ride, in mid-October. Enjoy the beautiful foliage of Central and Upper Bucks County, PA, and travel through up to six historic covered bridges. Don't let the ~2,800 riders worry you: with five routes (63, 50, 33, 30 and 20 miles), the roads aren't crowded. (http://www.cbbikeclub.org/?body=cove...6c7802c1236f0c)

Incidentally, one of the most comprehensive and up-to-date lists of events is maintained by the SCU webmaster, so you might want to check there occasionally.