If you are a South Park fan you probably know that there are several websites where you can watch episodes online. Most of them, however, tend to have broken links, poor quality videos and very slow servers. Even the official Comedy Central website was below my expectations.
One website that appears to have an edge over the competitors is South Park Zone. They have pretty much all the episodes from all the seasons, and the video streams fast and the quality is reasonable. Once in a while there is an annoying full screen ad, but other than that the user experience is good.
By the way, even if you are not a South Park fan try watching a video or too, I am pretty sure you will like it, so check South Park Zone!