One non-profit project that I find particularly successful in reducing a variety of prejudices is the Big Brother Big Sister Program. This program, started over 100 years ago, pairs children, ages 6-18, facing adversity with adult volunteers who guide these children, provide positive experiences and give these children someone to look up to. Although the pairings, themselves, are not necessarily arranged as a way of bringing two prejudice groups together, the adults and children involved in this program come from all backgrounds and walks of life and bond and interact so that the reduction of any preconceived prejudices between these two different people is made very possible. Although the program is ultimately intended to better the lives of the children, the adult also has the potential to gain and learn a lot from the Big/Little sibling relationship.
Here is a link to a page describing their mission, main goals, and their successes.