If you mention server-side scripting in most Web builders' presence, only one word comes to mind: Perl. This powerful and extensible language has rightfully earned a warm spot in Web developers' hearts and is almost certainly the most widely used scripting language on the server side of the Web today.
I don't use Perl. In fact, I don't do a lot of server-side scripting. But I'm about to, and when I do, it's more likely to be with Python than with Perl. Python is the most elegant, powerful scripting language for the Web that you'll probably never use.