If you've every tried to find green tweets and twitter users by searching for "green" at Twitter and been left wading through endless pages of irrelevant results due to the stupid ambiguousness of English, then you'll love this. Real-time feed of tweets on green, sustainable, and clean tech topics without the irrelevant results.
Web 2.0
Green Tweets: See what the green community on Twitter is saying in real time
Scoodi - give throw away culture the toss
Scoodi is a trading site dedicated to the re-use of the stuff we already have, and long term "stuff" sustainability. Scoodi is different, its hyper local which means reduced transport, its a long term inventory so you you can list things and relax; and you can go looking for things when you are ready. Scoodi is free, easy and fun because sustainability is important. We hope Scoodi is useful to the tree hugger community.

Send your Earth Day pledge to Planet Earth, c/o Ed B. and TerraPass
Post your Earth Day pledge in a "card" addressed to Planet Earth. Fun to read what other people are promising to do!
The future is green, open source and Nintendo
Its worth stating, again, what is really the blindingly obvious - thin-client work stations use one-twentieth of the power of a typical PC (10-20 watts versus 200-400 watts), require no maintenance or technical per-machine support and Open Source software is free of licence costs.

Green Social Bookmarking
Hugg is the best site for green social bookmarking but where else can you go to bookmark green?

10 Eco-Harmful Things that Web Writers are Guilty Of
Web writers should do their part to reduce their energy use and recycle their waste but many of them make these ten mistakes that harm the Earth.
How To Start a PSS, a Product "Service" or "Sharing" System, Part 1
An ongoing series about how to design a system to share goods that you probably shouldn't be buying -- clothes swaps, DVD and game rentals, freecycling and other networks. The more people share, the less they buy, so these systems let you reduce energy consumption and cut back on landfill use. Big self-promotion disclaimer -- I'm the author of this series!

Social Media Secrets from a Green Geek
Beth Kanter, all-around genius and social media goddess, talks with Jonathon Colman of The Nature Conservancy to discuss the secrets behind how non-profit organizations can better leverage web 2.0 sites like Digg, StumbleUpon, and Twitter to reach their supporters and create social change. GREEN + GEEK = GOOD!
The value of old-fashioned ways in a Web 2.0 world
I’m not making the big rant about going green but yes, it’s a problem and every contribution you can make on a regular and habitual level will help extend what’s left of this sputtering planet.

We Won't Be Doing Much Business On A Dead Planet
Inspiring article by Christophe Poizat, founder of the International Network of Social Entrepreneurs, about the rise of social entrepreneurship and a the new business paradigm that is necessary if we are to avoid the destruction of our planet.

EcoBlogs.net - Social Bookmarking for the Environment
Ecoblogs invites all green bloggers who blog about the environment, green issues, renewable energy, global warming or anything related to being green to use our new free Web 2.0 bookmarking service.

The 3 Commandments of a Top, Green Blogger (and Digg-er)
2. Grasp - quickly - the content that everyone else misses Scour and break top environmental news, yes, but also check out what your activist, researcher and even police (crime and traffic will always make news) friends are up to - they are usually the first with their eye on the latest news-worthy content.
Tip: Search the forums on places like Meetup.com to see what other environmental and special interest groups are talking about.

7 deadly blog sins thou shall not commit on thy eco-blog
Sustainable Community Action, a wiki for everyone interested in sustainability
Sustainable Community Action aims to link up community and personal action for sustainability worldwide. Its content is licensed under GFDL, so it can be reused by anyone else, and we are volunteers building information and networks about sustainable lifestyle.
Some relevant features are: its software, the same one like Wikipedia, its flexibility, you can advertise, even organize your actions using the wiki, and its compatibility with inclusion of Youtube videos and GoogleMaps, that enables you to make a green map of your town or city, or bring a video from a conference or piece of news.