It was suggested on a blog whose name I can't remember that a professional developer should learn at least six programming languages. Reading this, it struck me all of a sudden that I've been picking at the buffet without really committing to anything, as of late. So to take six and focus on them exclusively seems like a good idea.

There are, however, a few points to keep in mind when deciding this sort of thing.

"A language that doesn't affect the way you think...