The Pragmatic Programmer suggests learning a new programming language (at least) once per year. Specifically, you should learn a language that changes the way you think about things - learning C# if you know Java doesn't count.[Joe's Jelly]

I've been debating this myself. My problem is that I try to learn about three languages a year, hence, 6 years after I first started learning Python, I haven't done anything useful with it. And that's part of learning a language; it doesn't do you any good to just read the book, you've got to do something with it. So I'm conciously trying to limit myself this year. I've already decided that my new book buying this year is done: I've got The Python Cookbook, ANSI Common Lisp, and How To Design Programs. That I'm limiting myself to those 3 probably explains my problem. However, given the list, it's likely that the language of the year will be Python, Scheme, or Lisp. Python is probably the most practical, and I already have a passing familiarity. I started learning some Scheme last year so I've got a bit of a head start there. But I read the first 2 chapters of ANSI Common Lisp on Paul Graham's website, and half the 3rd chapter as previewed on Amazon, and I have to say that Paul got me excited about learning a new language for the first time in a long time.