I recently wrote a book that gives an overview of greywater systems, design considerations, and then includes how-to projects for building some of the most popular types of systems.
The book is called The Water-Wise Home: How to Conserve, Capture, and Reuse Water in Your Home and Landscape. (This book also covers rainwater capture and composting toilets.)
There is also the classic "Create an Oasis with Greywater" by Art Ludwig.
Greywater Action has lots of on-line info and system examples, and we hold workshops.
Co-founder: Greywater Action, www.greywateraction.org
Author: Greywater, Green Landscape, and The Water-Wise Home: How to Conserve, Capture, and Reuse Water in Your Home and Landscape