Alan Perlis said: A language that doesn't affect the way you think about programming, is not worth knowing. But I believe that the inverse of this is true as well. It is worth learning a new language if it can give you new ideas about programming.

In the same vein, Eric Raymond said in his How to Become a Hacker essay: But be aware that you won't reach the skill level of a hacker or even merely a programmer if you only know one or two languages — you need to learn how to think about programming problems in a general way, independent of any one language. To be a real hacker, you need to get to the point where you can learn a new language in days by relating what's in the manual to what you already know. This means you should learn several very different languages.

Likewise, it is possible to be a Real Programmer without using any programming languages. See The Story of Mel :)

For me personally, my job currently involves programming in Perl, Java, Javascript, PL/SQL and (blech) VB. Plus languages like XSLT and SQL that aren't really "programming" languages. I also like Haskell and have toyed in the past with Lisp, Pascal and Standard ML, (update oy, how could I have forgotten C?!) and have decided I probably ought to learn Python and/or Ruby also.