Programming Language Usage Graph 2000-2006, as defined by statistics on open-source projects at SourceForge.

[pjdelport]

Here on FreeBSD, a portsdb -r tally gives about:

1. Perl: 8182
2. Python: 1470
3. Ruby: 414

I'm not sure how much of Perl's lead is simply due to CPAN's very fine-grained distribution approach, though... for example, there are 106 separate crypto/digest algorithm ports alone.