The National Center for Science Education (
www.ncseweb.org) is the focal point for protecting evolution as an essential part of science. Eugenie Scott, its Executive Director, recently published Evolution vs. Creationism: An Introduction (Greenwood Press, 2004). Another excellent book about ID is Creationism's Trojan Horse by Barbara Forrest and Paul R. Gross (Oxford University Press, 2004).
Full disclosure - I am on the board of NCSE.