Given your interest in mobile/web apps, my recommendation is to start with Eloquent Javascript then Dive into HTML5 and then DOM Scripting. With those three, you'll have a solid base for what the next 5 years of what technology trends will throw at you.

Eventually you'll need to start working more with stuff on the server side. Once that time comes, you'll know enough to choose the server side language that makes the most sense for you (my bet is that you'll probably end up choosing between Javascript, Python, Ruby or Clojure in that order).