If you want to be able to code up quick things for personal use that do not take much time....python rocks.
I've been thinking about learning some Python for quite some time.
But I will add, JavaScript is also great for this sort of thing. Probably the easiest language to learn and use, and all you need is a text editor and web browser (no IDE, no compiler, no setup).
edit - I also must point out, Java and JavaScript are two entirely different languages. The reason I bring this up is because a lot of people, including a lot of computer people (which is sort of surprising) seem to think that they are the same language, or at least closely related to one another when in fact they are not.
(Both could be useful to web development, though from my experience I'd say that JavaScript is far more useful for that.)
And I see somebody here brought up assembly language. I would have to advise against that, assuming the original poster is not too experienced with programming and just wants to focus on web development. Because assembly language is awesome and great to know, but it's also very intimidating and confusing and not exactly relevant to the web.