SopCast is a program that allows you to watch video streamed by other people across the web. It basically acts as bittorrent, but just for video. You download a stream as you upload it to someone else. The quality's not great (especially in fullscreen), but it's good enough for a smallish window while you do other stuff. Here's a link to some MLB games, but they've got lots of other sports too. This site is pretty euro-centric, so I can use it to watch EPL or Bundesliga matches, but they've got most major American sports as well.