From Envirowiki

thematically similar wiki projects to Envirowiki:

• Tip the Planet provides practical tips on how to act environmentally aware in everyday life
• Greenlivingpedia collects information on sustainable and environmentally friendly "green" living
• Appropedia is a popular wiki that collects knowledge on appropriate technology for collaborative solutions in sustainability, poverty reduction and international development through the use of appropriate technology and the sharing of project information. (They also have a list of green wikis.)
• Overview of wiki on environmental topics at Wikia