I'm one of the people you mentioned who is a big proponent of C/C+ and Java for web apps, but i do have some experience with Python and IMO its a great language for scripting and has good integration with C programs, but it isnt that widely used and you probably get more mileage out of learning other languages. As for smalltalk its somewhat outdated and hard to program in due to its "everything is an object" design and has virtually no industry uses.

If you really want to learn something besides C/C++, Perl is an excellent choice. Not only can it be used for scripting it also can be used to write full fledged apps. Its great for database programming and if your an open-source advocate there is no limit to what can be done with the "LAMP" grouping of technologies: Linux, Apache, MySQL, Perl and PHP.