Some (repeat Some) of the ones I visited a few weeks ago:
http://www.blaauwklippen.com/
http://www.kleinconstantia.com/
http://www.vergelegen.co.za/
A friend also suggested, although I did NOT visit;
http://www.kanonkop.co.za/the_wines.htm
If you are looking for someone to connect with to do a more "proper" tour, let me know - so I can connect you with the people I used. Otherwise I'm assuming you will just drive from place to place on your own.
[This message has been edited by NickP 1K (edited 04-18-2003).]