Green Home Idea: How to convert my house to reclaim Graywater to use for lawn irrigation?

I want to conserve water and use graywater from my sinks and showers and maybe runoff to irrigate my landscape. This would help offset my use of clean water and still allow me to have a nice lawn. Has anyone done this? How to I do this, how expensive is it, and what health hazards/water treatment do I have to worry about?