Ebuild
http://www.ebuild.com/
Directory of building products and manufacturers. Not restricted to green building materials.

EcoBuild Web Ring
http://x.webring.com/hub?ring=ecobuild
For research and information groups dedicated to improvement of the built environment in balance with the natural environment.

GreenSpec: The Environmental Building News Product Directory
http://www.greenspec.com/
Directory from the publishers of Environmental Building News.

Materials Analysis Tool (MAT)
http://www.materialanalysis.ca/
A free online ranking system that distills manufacturer information to assist in the selection of building products that are more cost effective, healthy and environmentally responsible.

Oikos
http://oikos.com/
Serves professionals whose work promotes sustainable design and construction. Includes an online library, a product directory, and a bookstore.

Wisconsin Built Directory of Energy Efficient and Sustainable Building Products and Services (Madison, WI : Wisconsin Green Building Alliance, 1998)
Directory of Wisconsin-based suppliers of green building materials.