Most programmers have worked with at least a few different programming languages. Those who are as ancient as I have likely worked with many. Some programmers have a nearly religious attachment to their One Right Language; others are less concerned about the language than they are about the algorithms and data structures. I'm definitely in the latter camp.
Recently I came across this web site, which attempts to rank programming languages by the number of programmers who use them – measured indirectly by the number of web searches involving them.
I was not surprised to see Java in the number one slot, nor was I surprised that C and C++ took the next two slots. This measure has those “big three” taking 50% of the total search hits. Everyday experience says this can't be far off the mark, as virtually everyone I know professionally works in one or more of these three languages.
But even more stunning to me is that Delphi (which evolved from Pascal) and Pascal itself are having a bit of a resurgence in popularity. I did a lot of development in Pascal back in the '70s and '80s; it was the first high level language that I really enjoyed using (I was a real assembly language cowboy back then!). It was also my introduction to object-oriented programming (via Borland's Object Pascal). I'd never have expected them to be on the rise...
One last personal reaction: the chart makes me feel a little old, as most of the languages I've worked in aren't on the chart at all. Assembly language is gone. Remember dBase, anyone? PL/1? Pogo? B? CMSII? And yet...I've worked in 12 of the 20 languages on the chart (counting even casual encounters). Yikes!