For non-programmers: you don't need to know 5 programming languages. 
Knowing one is probably enough, and I would suggest Python. Then you 
may need to know things like Visual Basic for Applications or 
JavaScript.

For programmers, different languages are useful as a way to learn 
paradigms. I would suggest:

    A low-level procedural language such as C. It helps you understand 
the machine, and there is a very valuable body of code written in C you 
will want to study at some point. C is also the language of Unix, and 
understanding Unix may be more important than knowing any programming 
language at all.

    A Lisp, if possible a Scheme like Racket. It will introduce you to 
fundamental concepts like dynamism and homoiconicity. Study how to 
implement Lisp in Lisp, then study how to implement Lisp in C. This 
will teach you about the relationship between the teoretical part of CS 
(lambda calculus) and practice (how real computers work). It will also 
help you understand the power of well-chosen simple mechanisms.

    A language to get real work done. Depending on your field, this may 
be Python, Java, JavaScript, Objective C... This is the language you 
use at work. Something solid, dependable, probably with a reasonable 
amount of libraries you can leverage to get things done.

    A concatenative language, probably some variant of Forth. 
Concatenative programming is a paradigm that is not known well enough 
and yet embodies several fundamental concepts of CS. Although it has 
influenced fewer languages than Lisp, it is the same kind of simple 
language that opens your eyes.

    The last slot depends on what you want to do. Haskell will teach 
you about types, Erlang about distribution, Self or Smalltalk about 
OOP, Prolog about Logic Programming...

I cannot write an answer like that without mentioning Lua. I didn't 
include in the "top 5'" list but you should still have a look at it, as 
a language that is extremely well designed, simple, fast...