See here for an overview: Re: Next Language to Learn (and the related thread)

You may also have a look at the Tiobe Index, which gives a popularity-ranking of programming languages. So you can choose one that is "en vogue".

(Be however warned that the way the index is computed is highly questionable. See Re: Perl is sinking (TIOBE): all time low for Perl for a critical evaluation by moritz.)

HTH, Rata