Pedals for Progress ships bikes to developing countries around the world. Their plan is that they try to get community organizations to do a one-time (or once yearly) collection rather than have a donor site. If you belong to a church, Scout group or similar group that wants to do this, there is contact information at their website to help you set it up, or call 908-638-4811.
Bikes not Bombs at 59 Armory Street in Roxbury, 617-442-0004 does similar work.