Well. I'd say learn C and javascript. They are most widely used languages.
You might want to learn Java/some .Net language and/or python/ruby: they're more convenient, tho.
This have the advantage that all those languages are reasonably well designed.
For example, don't learn PHP or C++ because they're a mess. They're used widely, you might want to learn them one day, but they can seriously mess with your mind.
