Note: See bottom of post for some other streaming options!
There are a few options to do this(jtvlc, webcam studio), but the easiest is to use the built-in streaming application on the justin.tv website. The reason this doesn’t work out of the box is because of a bug in flash that results in flash not prompting for access to system devices on linux. To get around the bug you need to allow justin.tv to always be able to use flash to access your webcam. To do this visit the site below:
Now, scroll down until you find a url that looks like www-cdn.justin.tv. Highlight the link and then populate the “Always allow” bubble. It should look like the screenshot below when you are done. After you have done this you can visit the justin.tv site and stream using their webapp.
You can also stream to justin.tv using the instructions in the link below:
In response to the link above, my justin.tv command eventually looked like this:
sudo ffmpeg -f video4linux2 -s 640×480 -r 15 -i /dev/video0 -f alsa -i pulse -ac 1 -ab 96kb -ar 22050 -r 15 -b 550kb -f flv “rtmp://live.justin.tv/app/live_12398123_asdf123”