Heading to, say, India and want to bone up on your Hindi (or your Malayalam, Kannada or Oriya)? These books can help:
How To Learn Any Language by Barry M. Farber
Learning Foreign Languages: Everything You Need To Know by Brandon Simpson
The Quick and Dirty Guide to Learning Languages Fast by A. G. Hawke
Why You Need a Foreign Language & How to Learn One by Edward Trimnell
The Loom of Language by Frederick Bodmer