Zandvlei Trust
This volunteer organization manages environmental concerns within the Sandvlei catchment area. This area is important because it is the healthiest of all the wetlands in the Cape Metropolitan Area, in spite of being heavily urbanised (Marina da Gama, Westlake, Kirstenhof, Retreat) and heavily used for recreation (Sandvlei and Marina).
The website addresses broader issues than just the road, but the section on the N21/R300 Toll Road is on this page, which also serves as a wonderful summary of the issues and provides simple steps to take and contact information that you might need. The Zandvlei trust has been instrumental in helping coordinate the protest against this road and I liase with them continually.
Peninsula Expressway Consortium
These are the people proposing the road. Beware that you will not be able to browse the site without Windows and Internet Explorer (the menu doesn't work for me on linux). The Downloads page on this site is very interesting. It contains write-ups of interviews with Interested and Affected Parties (specifically experts in their fields that requested an audience). It is surprising how many times the developers and environmental consultants incriminate themselves when responding to questions.
For example: When Mark Dittke, an environmental lawyer, asked for proof of the validity of the road traffic models used by the consultants, they went to great lengths to convince him (without actually showing him the models) that their models are valid. When he then asks how traffic flow might degrade the environment as a result of people using alternative roads to avoid paying a toll - they say it is impossible to model something like that. How do they come up with a model that shows exactly how many cars need the road, but cannot tell you where the cars would be if the road weren't there?
Mountain Mist self-catering Cottages Birding and Fynbos Retreat on a mountain top in the Western Cape, South Africa
This site debunks the incorrect information published by the official Mountain Mist website, such as easy access to bushman caves and exclusive use of a shared pool. It is listed here as a public service to alert nature lovers about the danger of staying in this resort. It describes some of the unpleasant and occasionally dangerous experience a neighbour has had with the owners of this property.