HTML/PHP & MySQL, GML (trust me, it's a sucky language to know cause it's COMPLETELY USELESS outside of Game Maker, but still, I'm listing it cause this ain't a resume), C#, working on Java next semester (starts on the 8th of january).
Some vb.net, not listing it though. It's not a language I ever want to use outside of the "quick & dirty calculator" assignment we did in class >_<
COBOL's the really useless one; I don't even have a compiler for it anymore. And yet I like it better than vb.net and it reminds me too much of basic, especially where it's the whole "this then this then this" thing instead of "on mouse click do this, on mouse over do this" event driven thing.
And I'd define knowing a language as being comfortable and understand the basics of the language (if you can't declare a variable for instance, you don't understand the basics). Add bonus points if you know a place you can check to get answers you don't know.
php.net, for example, kicks bootay when it comes to php. And if you understand the basics, you can turn this:
bool imagecopyresized ( resource dst_image, resource src_image, int dst_x, int dst_y, int src_x, int src_y, int dst_w, int dst_h, int src_w, int src_h )
into this:
imagecopyresized($display_image,$copy_image, 0, 0, 0, 0, imagesx($display_image), imagesy($display_image), imagesx($copy_image), imagesy($copy_image));
(resizes the image found in resource $copy_image down/up to the size of $display_image, usually followed up by a few headers and some form of imagejpeg/imagepng/imagegif to display the image).
I use that site every single day. But I also know the basics of php enough to know what in the blue hell all those arguments mean, therefore I consider myself to have known the language ^_^
Someone's gunna call me a 'tard though, I can pretty much guarantee it. Cause by my logic if you know how to turn the wheel, shift gears, and step on the pedals, you know how to drive a car >_<
Edit: And is anyone else NOT surprised that php has 9/10 voters saying they know it? It's a free webhost that supports php, why not learn it XD
And some of GML (Game Maker Language 
