I second Arunbear's list, but would add my preference for
. In my last job I learned (scratched the surface of) python and grew to like it quite well. I don't believe Python was built to be a web development language, but it certainly can perform in a web environment well. Similar to Perl's "mod_perl" package which builds a perl interpreter right into the webserver process(es), "mod_python" does the same thing with the Python interpreter, so performance is good. Python is not as mature as Perl, but what other language (besides C) is ?? ;-)
It's been a few years since I've used PHP, but when I did I came away really liking it. PHP *was* built to be a web development language from the ground up. The standard PHP installation comes with lots of stuff that other languages like perl require additional packages for, like session handling and more (that I can't recall right now). And, PHP is blazingly fast.
Just my 2c.