C# FTW!
I haven't written anything in DarkBasic or any other BASIC variant in a long time, I'd rather use DarkGDK. Mainly I write stuff in C#, C++, and ActionScript 3 (Flixel ftw). Though lately I've started playing around writing scripts in Ruby and Python for fun. I've also learned some Scheme and Lisp from the SICP videos and from trying to make Emacs convert tabs to spaces.
Will be working on learning Objective-C, Lua, and Javscript in the future. A little PHP too, but only grudgingly.
As far as the value of writing in/knowing multiple programming languages, it's definitely a good thing overall, especially if the languages use different programming paradigms and/or approach these paradigms in different ways. It'll teach you to think about how you're solving your problem in a deeper way.
One exception though: working with C# and then going back to Java is an awful, painful experience.