Many YahooGroups feature a user generated links page.

 

I've put links to WiserEarth onto the YahooGroups that I belong to, using this text copied from WE homepage

 

"WiserEarth . . .

serves the people who are transforming the world. It is a community directory and networking forum that maps and connects non-governmental organizations (NGOs) and individuals addressing the central issues of our day: climate change, poverty, the environment, peace, water, hunger, social justice, conservation, human rights and more. Content is created and edited by people like you."