Many cities contain subcultures of bicycle enthusiasts that include racers, bicycle messengers, bicycle transportation activists, mutant bicycle fabricators, bicycle mechanics, and bicycle commuters. Some such groups are affiliated with activism or counterculture groups. These hybrid groups often organize activities such as competitive cycling, fun rides, protests, and civil disobedience, such as Critical Mass. Some groups work to promote bicycle transportation (community bicycle program); others fix bicycles to give to children or the homeless (Bikes Not Bombs). There are also feminist groups of women of color who promote the empowerment of women through their rides such as Ovarian Psycos.