http://bogy.mine.nu/sc2/stream2vlc.php

Summary (aka modified copy/paste):
1.) Get VLC http://www.videolan.org/vlc/index.html
2.) Get rtmpdump https://github.com/svnpenn/rtmpdump/downloads (the one on top)
3.) Go to http://bogy.mine.nu/sc2/stream2vlc.php
3a.) In the following fields enter:
3b.) Channel name/ID#: Name of channel (ex. platinumtf2/gavinc27/cyzerr)
3c.) VLC local path: The path to your VLC executable. (C:\Program Files (x86)\VideoLAN\VLC\vlc.exe)
3d.) RTMP local path: The path to rtmpdump.exe (Which you just downloaded)
3e.) click the button and copy to output to the console(cmd) and watch the stream on VLC!

Why would you want to do this? Uses way less CPU that the shit flash player on jtv.