Right now, when I'm at work, I'm focussing fully on PHP development. This will be changing though. It has been decided that the whole backend system is going to be re-written in JSP.
Luckily, instead of just firing the PHP coders and hiring JSP coders, my employer scheduled a JSP course in January. So I'll soon be learning JSP. I'm quite excited about this, because of the many good things I've heard about JSP, amongst which it being quite powerful.