Permaculture, the Soil Association and the Centre for Alternative Technology are to be mentioned first because they have more than opened my eyes to the prospect of saner modes of living.
In Kent and the South East, Hadlow College, Commonwork and the Sustainability Centre stand out on their own merit. Of special interest, the Butser Ancient Farm. Yes, an ancient farm in Hampshire!
These two links - the Sustainabile Building Association and Canterbury's School of Architecture - are about building and energy, and about hand-based skills 'lost in today's electronic world'.