There is already a lot being said about sustainability. The thing for designers is that sustainability touches every single aspect of their design. It's not just clean energy, or eco-friendly materials, or ways of dealing with waste - but it's all that, plus several other issues. And if a designer is trying to put sustainable thought into action in his design, it's important to keep an overview of all the issues at stake.
the Danish website sustainablecities.dk is thus a very noble initiative in my eyes: it's a platform for all kinds of sustainable issues in thinking about cities and making cities. It displays cases and topics of all sorts, lists experts, gives way to various discussions. The content of the website is clearly in a development phase, but the initiative is clearly worth everbody's attention - if you are even remotely concerned with sustainability issues, that is.