As a kid my parents would take the family to Spain for a good part of the summer. I became quite fluent while there.
As the trips changed over to other non-spanish speaking destinations the capability to speak faded. However, many years later, when relatives would visit the language would gradually come back to me. So, I agree with putting yourself in an environment surrounded with what you want to learn.
Also, I believe this may be the type of aid you asked about
:
http://www.pimsleurapproach.com/learn-spanish.asp?