What is the best way to clean makeup brushes?

My days of not washing my brushes have caught up to me as I'm starting to break out bad. I'm desperate for efficient cleaning methods.

EDIT: Thank you everyone for your suggestions, I really appreciate it. I cleaned my brushes last night with some dish soap and my mug looked like freshly brewed coffee. Today I purchased a bottle of Tea Tree Castille soap at Target for a reasonable price. These responses were very enlightening.