Fullscreen YouTube was limited to Mac/Windows until very recently. The new (released 2 weeks ago) Adobe Flash Player works with it. To install it, run each of these commands one at a time. Please note that the wget one goes on to the second line because the URL is so long. That command starts at "wget" and ends at the first ".tar.gz".
cd ~/Desktop wget http://fpdownload.macromedia.com/get/flashplayer/current/install_flash_player_9_linux.tar.gz tar xf install_flash_player_9_linux.tar.gz cd install_flash_player_9_linux/ sudo ./flashplayer-installer
Now copy this down into gedit or something because it'll tell you to close the web browser. When it asks for the install path for the browser, if it's Firefox 2, put /usr/lib/firefox If it's Firefox 3 and you're fully updated, put /usr/lib/firefox-3.0-3.0b1 If you're using Konqueror with KDE3, it'll be /usr/lib/kde3 but it'll probably tell you that's not a valid place to put it because it doesn't have a plugins and a components directory, so then it'll assume Opera, won't find that, and will assume Netscape, and won't find that. You can trick it into thinking it's installing in Firefox by doing
sudo mkdir /usr/lib/kde3/components/ If anyone knows where Konqueror for KDE4 and Epiphany go, leave it in a comment. I don't have those installed.
EDIT:Or since Hardy has a working deb, download the Flash package for Hardy.
If you're using Compiz Fusion, turn off "Unredirect Fullscreen Windows" in the General section and turn off "Legacy Fullscreen Support" in the Workarounds plugin. If you don't, the controls for the player get cut off.