Yes, there are.
Big ones:
http://tour.diabetes.org/site/PageServer?pagename=TC_homepage
http://main.nationalmssociety.org/site/TR/Bike/TXHBikeEvents?sid=3590&type=fr_informational&pg=informational&fr_id=17896
There are a lot of charity rides for trails around here. E.g. September 22nd Tour De Montour -- http://montourtrail.org/events/index.asp