Centaurs were horses with the upper-portion of a man's torso where a head would normally be. They were generally considered to be uncivilized, and that was why they were part beast. All centaurs were male.
Cheiron--"The Great Teacher". He was more humane and civilized than most men, and taught many of the great heroes including Herakles, who accidentally killed him. After his death he was put into the sky as the constellation Sagittarius.
Nessus--He tricked Herakles into letting him carry Deianira accross a river, and planed to abduct her before Herakles could cross. Herakles found out, and shot Nessus with an arrow. Before Nessus died he told Deianira that when applied to a cloak, his blood would make the wearer of the cloak love her forever. She believed him. She put it onto one of Herakles' cloaks, but instead of making him love her, it burned his skin, and to escape the pain he was forced to kill himself. Deianira hung herself after finding out what she had done.
Pholus--While chasing a boar, Herakles stoped at his house and ate dinner there. All was fine and dandy until Pholus hesitated to serve the Centaurs' common wine with the great hero. Herakles insisted, and Pholus served the wine. The other centaurs smelled the wine, and fought Herakles for it. He killed or chased away those who attacked him. Pholus died in the battle, having droped one of Herakles' poisoned arrows on his own foot.
Eurytion--He tried to violate king Dexamenos' daughter, but Herakles rescued the girl and killed Eurytion.
Elatos--The Centaur that Cheiron was protecting when Herakles shot Cheiron.
Abas--A skilled hunter.