I learned and have been payed to program in way too many languages. Just as I have read many many books. But the question is - which languages had a lasting impact? Which languages brought me insights that I wouldn't have gotten without learning those languages? Just as with books? Which book that you read do you remember now? That's the question to ask.
My main languages are Common Lisp and C++. The expressive power of Common Lisp is beyond anything I could have imagined without learning the languages, and the things that people do in this language. C++ is more of a love-hate thing. It's like wrestling I guess. It's pain and it stinks but if you are successful you keep doing it. I do high-performance computing, so I don't use any of the runtime features of Common Lisp (I only use it for it's advanced compile-time computing, after macroexpansion the code looks like C code). C++ is obviously the weapon of choice of you want runtime-overhead free code.
Among the scripting languages Perl, Ruby and Python I really don't like any of them, but Ruby offends me least. I still know Perl better, though. Python broke backwards compatibility with the latest version, I should check it out. Python has a large community coming up with stuff for Python that makes it interesting, too. Ruby on the other hand seems to finally go SMP-capable interpreter in the CVS versions.
I know bourne shell very well, used to maintain an implementation. It's very useful to be good at it since you can write mini-programs right in the commandline, then echo them to a file and edit the file to make a script. Obviously it's an insane language, though
I learned enough functional languages that I know they don't fit my brain. It's like square key and round hole. Sorry chaps.
I will never learn languages that are available only from one non-open source vendor. What do you do when they take it away?