As far as I know, and I've done a lot of searching, there's nothing comparable to Sopcast for Mac. But there is a solution...
I'm in France for a year and want to watch NFL football. I searched desperately for a solution for the Mac because there are sites that stream games through Sopcast. Short of bootcamp and that whole mess, there's not much esle to do. Except Crossover!
This application is only in beta phase, and not many applications are supported, *but with Crossover you can run Windows applications on your Mac* without buying Windows. And you can run Sopcast on it. *In order for it to work though, you have to install it in a Win98 bottle with Windows Media Player 9 in the same bottle.* You can also use VLC for mac to stream from Sopcast (you have to have both running) and there are plenty of tutorials on how to do this. Just make sure you put the stream on a loop while using VLC or it will keep stopping after a few seconds.
I hope this gets out there. *Post freely on other forums as there is not much info. on this subject.*