The purpose of this post is to get some advice/recommendations from some other developers on what path to pursue next to progress and improve. I am trying to decide what programming language to learn next, and currently im edging towards C++ but considering some dialect of LISP maybe scheme or a JVM language like groovy or scala. I have also thought it may be worth while adding an interpreted language to my toolbelt like perhaps Ruby (python syntax doesnt click with me). My main requirements are that it should run on any OS, in most environments and have a decent amount of documentation/learning material.
What do you think? I know there is no one correct answer but, i think some advice/contributions of some of your past experiences may push me into making a decision.
A bit of info about myself:
I am primarily a .NET Developer therefore very comfortable with the 'Microsoft' way of development and using their stack IE C#, .NET Framework, MSSQL etc... in a web environment mainly, but also played around with WP7 and some small desktop apps. I also can get by in Java (mainly from looking at it at Uni). Bare in mind i have just bought a macbook to force me to purse other technologies/languages (although i still do work development in a windows on a VM).
Many thanks in advance.