Skiing is not that big in South Africa, as we don't have much in the way of snow, there is, however, one dedicated ski resort, near Rhodes, that has guaranteed snow between July and September and offers grass skiing in the summer.
There are other places where one can ski like the Sani Top in the Southern Drakensberg Mountains, but none of these are formal areas so you have to really be keen and adventurous. If you have the money and are lucky with the snowfall, there is some wild and unchartered heli-skiing to be had, in the Western Cape, but the runs are not that long.
We make up for the lack of snow by having wonderful sand dunes - you can try sandboarding near Cape Town or Port Elizabeth. Sandboarding is an exciting extreme sport, which is easy to learn.
It is similar to snowboarding and surfing but doesn't require layers of clothing or wetsuits. Probably the biggest attraction of sandboarding is the relative ease of learning. An absolute beginner will pick it up within a day, given the right instructor. Turns, small jumps and high speed are commonplace on the first day.