This video describes at a high level what it takes to configure Ubuntu 11.04 ssh access to require a verification code from Google Authenticator. Here are some useful links:
WebbyNotes Guide:
http://guides.webbynode.com/articles/…
Guide by Jean-Francois Theroux (Installation / Configuration):
http://blog.theroux.ca/security/ubunt…
Download the Ubuntu Google Authenticator package for Ubuntu:
https://launchpad.net/ubuntu/+source/…
Background can be found here:
http://gnome-look.org/content/show.ph…
YOUTUBE VIDEO LINK
http://www.youtube.com/watch?v=UTjdW3F6GOc
Netclad Security 