YSC Tour de Pink (haven't seen an announcement yet for 2011)
Bike4Breast Cancer Ride (haven't seen an announcement yet for 2011)
The Livestrong Challenge
American Cancer Society Bike-a-thon Philadelphia
You might also want to check the list of charity partners for the Five Boro Bike Tour once they are announced.
Look into the Pan Mass Challenge - 2011 will be my third year riding. All the money goes to Dana-Farber Cancer Institute, the event raises more money than any other athletic fundraising event in the country - $303 million since it started back in 1980.