You would need to add the Handbrake repository to your sources.list to get handbrake. It is a bit easier than it appears.
Originally Posted by MetaMs
Open a terminal (Applications > Accessories > Terminal) and type
Add the following to the end of the file and save...
gksudo gedit /etc/apt/sources.list
Then add the authentication key - copy the contents of the following webpage to a text file on your desktop.
deb http://ppa.launchpad.net/stebbins/handbrake-snapshots/ubuntu lucid main
deb-src http://ppa.launchpad.net/stebbins/handbrake-snapshots/ubuntu lucid main
and go to System > Administration > Software Sources > Authentication and import the key file that you just created.
Reload your software sources and you will be able to install handbrake using Synaptic Package Manager.