Cyburbia: ubersite linking to all manner of planning and architecture resources [ta Phil].
Congress for the New Urbanism: replacing spawl with communities, promoting environmental conservation, and operating at all levels from the street to the metropolis.
Carfree Cities: how to copy without cars, but also how to restructure our cities to work well with this.
What worries me about many of these plans for new cities is that they're very top down, building the city and then getting people to move in. How about a set of rules, or guidelines, that can be started at any moment of a city's development (which is always), and that work towards a "better" place? It's gotta be bottom-up baby. Carrots and sticks, all the way.