[nmjohn]

All three are viable candidates - however because it appears to me like you are trying to learn more about web development, I'm going to suggest node.js, because like it or not, when it comes to the browser, javascript is your only choice for the foreseeable future.

This way you don't have to expend any extra energy on the cognitive overhead of switching between languages when you switch from writing something in the client side app and then something on the server side. To be fair to the other languages, I don't think this is a huge issue in day-to-day development, but from my experience is was an enormous issue when I was trying to learn a new language and I actually had to think about the syntax I was writing.

My biggest suggestion though is not to do it in java and instead expand your horizons - if I plotted my strength of a developer against time on a graph there would be long flat sections interspersed with sharp upward inclines. Those inclines? For the most part, short periods of time when I started working on learning to program in a new language.