Reminded of Project Euler by Seth Tisue's Project Euler work, I figured it would be a good way for me to start learning new languages, too.
Seth says: "If all the pure math gets old try poker (no. 54), Monopoly (no. 84), or Sudoku (no. 96)" https://twitter.com/#!/SethTisue/status/107122784861306881
Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.
The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.