How do I install USB drivers in Ubuntu 13:04 for Nexus S? I am trying to follow this guide:
   http://forum.xda-developers.com/showthread.php?t=2163085

However I am unable to connect to my android phone via USB.  I think I need to install the USB drivers for Ubuntu.  I am using Ubuntu 13:04 and the Nexus S currently has Cyanogenmod on it.

Any help would be appreciated.

Thanks,
Glen.
As was already pointed out in a number of answers as well as in the comments, one does not need to download/install separate USB drivers for your Android device; they are already compiled into the Kernel.  However, you do have to tell your Linux system what device you want it to treat as such (udev rules in /etc/udev/rules.d/ directory).  Take a look at the Android Developer Site

To facilitate the installation of these "udev rules", I've set up a github repository with an installation script at https://github.com/ILMostro/Android-Udev-Rules.  You can download it with git by typing into the terminal:

git clone https://github.com/ILMostro/Android-Udev-Rules.git