SopCast Player is a Linux GUI front-end for the p2p streaming technology developed by SopCast. SopCast can play various TV channels for free, using the internet. It comes with its own channel list but you can find lots more on various websites.
Roberto @ Lffl has finally updated the Sopcast PPA to include packages for Ubuntu 11.04. The PPA includes packages for both 32bit and 64bit - there were some issues with the 64bit packages in other PPAs a while back but that was fixed in Roberto's PPA, hopefully the Ubuntu 11.04 packages will work on 64bit but I'm not sure since I've only tested it on 32bit.
Add the PPA and install SopCast Linux Player using the commands below (packages available for Ubuntu 10.10 and now 11.04 too):
sudo add-apt-repository ppa:ferramroberto/sopcast sudo apt-get update sudo apt-get install sopcast-player
Important: the "show controls" and fullscreen options don't work using the default settings. To fix this, in the Sopcast Player Preferences, on the "Player" tab, select "Use External Player" and under "Command" enter "vlc" (without the quotes).
You can also associate sop:// links with Sopcast Player using the commands below:
gconftool-2 -t string -s /desktop/gnome/url-handlers/sop/command "/usr/bin/sopcast-player %s" gconftool-2 --set --type=bool /desktop/gnome/url-handlers/sop/enabled true gconftool-2 --set --type=bool /desktop/gnome/url-handlers/sop/need-terminal false