I'd say that the market has a fair amount of jobs regardless if you start with node, golang, java, python, ruby, php etc.
From that list i'd say there's a good starting point to check out
I think you get the whole 'awesome programming language here' :)
And as always, since you're talking about backend development learn your SQL, This tutorial from Khan Academy looks like a decent starting point.
Also, you can have a quick peak at Todo Backend a nice complement to the todomvc or Hacker News clones
Especially the SQL point is something I actually haven't thought about till yet... even though it totally sense! And special thanks to all the links! Helps a lot!