I did Spanish and used Pimsleur. As opposed to Ro$$etta Stone this is a very inexpensive way to see if you are condusive to learning by this method (like $10). 30 minute sessions on 4 CD's - did it on the morning drive time. They sent me Vietnamese CD's the first time
I called and they quickly sent the Spanish out and told me to keep others - if anyone needs Vietnamese language CD's I am your guy.