'Sustainable design' as practiced in 2008 is very similar to what was called 'Appropriate technology' in the 1970's, perhaps best symbolized by the 'Whole Earth Catalog', but also involving a large network of people inventing very creative soft technology and lifestyle changing methods and ideas. Since those resources are mostly not online you can expect to discover lots of good stuff in the archives of some of the journals like RAIN magazine and Popular Science.
The main difference in today's version of sustainable design is its systematic use in architecture and planning in the commercial world. That is best symbolized by the enormous success of the LEED program of the US Green Buildings Council and the Green Globes industry association, and the US Federal Whole Building Design Guide, and the Athena life-cycle project impact assessment tool. There are now also numerous profit and non-profit product rating and selection web sites and large professional association design standards, such as the ASRAE engineering standard SPC 189. Many of these subjects are referenced on Wikipedia too, under either 'sustainability' or 'sustainable design'.
There are also a variety of methods and organizations aimed at the systematic application of deeper green design principles. They include BioMimicry, Archtecture2030, Cradle to Cradle, 4Dsustainability among others.
There are also major gaps in the 'appropriateness' of the technology being brought to bear, however. Though some long range models of environmental impacts show a reduction in the future, it's also broadly recognized that the main achievement of all this effort is just to increase our impacts on the earth more efficiently...! Nothing people are organizing to do is actually producing any total decrease in impacts, and the plans to change that are vague. The basic reason appears to be that money is our measure of value and it takes the economies physical energy and resources to produce make the choices we use it for, in direct proportion. Because that's confusing to most people, and leading organizations and public discussions are not good at exploring complex questions, the subject is little discussed.
--Phil Henshaw 09:22, 16 January 2008 (PST)