Google Chrome supports "web applications" which run in a dedicated browser window: no bookmark bar, tabs, and less UI in general. These are useful for dedicated windows such as web-based email, feeds, and now Ask Ubuntu chat. In particular for chat, new links open in a different browser window if you middle-click or otherwise select "open in new tab/window"; this keeps the chat window visible and handy.
Create a new file on your desktop, let's call it askubuntu-chat.desktop, with this content:
[Desktop Entry]
Version=1.0
Name=AU Chat
Exec=/opt/google/chrome/google-chrome --app="http://chat.askubuntu.com/?tab=favorite&sort=active"
Terminal=false
Icon=askubuntu
Type=Application
Categories=Network;WebBrowser;
Mark it executable:
$ chmod +X ~/desktop/askubuntu-chat.desktop
Grab a high quality icon:
$ wget http://sstatic.net/askubuntu/img/apple-touch-icon.png -O ~/.local/share/icons/askubuntu.png
The launcher name can be customized either in the file ("Name" entry) or on the desktop, and the URL can be whatever landing page on chat you find most useful. I like the room favorites because I can see any recent activity or use "rejoin all".
Desktop icons:
Less UI, handy rejoin button on first page you open:
The AU icon is also used for the Chrome window: