I love project Euler. A nice way to improve programming skills in a new language is to go through others solutions in the same language after you solved a probl

I love project Euler. A nice way to improve programming skills in a new language is to go through others solutions in the same language after you solved a problem. This allows to break bad habits. Say you are a C programmer learning Ruby or Lisp, 'C-ish' approach will often seem the most straightforward, but will rarely be optimal and idiomatic in the new language you are learning.