python
you should start with python to learn to concept of programming. Python is simple but also very powerful. you will start out learning concepts about programming and making simple programs, but you will end up making very elaborate applications. Because I'm a web developer I started with PHP but when I wanted to start making simple scripts to perform monotonous tasks I found myself learning python.
I would also recommend ruby, as much power as python but some say an easier syntax. Iff you want a harder language to learn than python or ruby I would recommend learning C mainly because C++ will give you too much rope to hang yourself.
Anyway at the risk of typing out another paragraph i recommend you read this top to bottom, and then decide weather or not python is worth learning:
http://openbookproject.net//thinkCSpy/
I'm also thinking we should make a sticky for these kinds of threads, detailing what has been outlined to other people seeking which is the "best" language to start with.