You really should not group C# with C and C++. Also, Visual C++ is not a programming language per se, but just the name that Microsoft gives to their IDE for C++.
You also should not have grouped, Java, JScript, HTML, CSS and PHP. Java has more in common with C# than anything else. Javascript is a client side scripting language while PHP is a server side scripting language. HTML and CSS are languages are not even programming languages.
SQL is a query language and it does not even exist in the wild. While there are implementations of it, each are different and unless you are using a variation with stored procedures, it is not a programming language in the slightest.
UNIX shell is not a programming language per se, but a command prompt, of which there are numerous varieties that all have different syntaxes. Each individual shell is a language in itself.
Also, I have no idea why you put Powerhouse and Squirrel on the list when you have omitted FORTRAN, COBOL and Lisp. FORTRAN and Lisp are largely the progenitors of modern programming languages, although COBOL is a highly important language in its own right and anyone who knows it is basically guaranteed a job for life, regardless of whether or not they hang themselves because of it. There are also BASIC, ALGOL, APL, SML/NJ, Smalltalk, Haskell, OCaml, etcetera to name a few.
Anyway, if you want to learn a new programming language, I recommend C++. If you have a solid knowledge of C, then learning C++ will be an extremely educational experience. C++ is a huge language that has nearly all of the features found in the categories of imperative, object oriented programming languages. Knowing C++ will make learning other languages in that category easy. At the same time, if you want to have a good knowledge of programming, you will also need to learn functional programming (e.g. SML/NJ, Smalltalk, Haskell, OCaml, etcetera) and also write a compiler. If you can write a compiler, then you will be able to write basically anything.
You also should probably be asking about book recommendations. Some good books are The Art of Computer Programming by Donald E. Knuth, the Dragon Book (google it), The C++ Programming Language, The C Programming Language and The UNIX Programming Environment.
If you have not stopped using Windows already, I recommend switching to a UNIX OS like FreeBSD. Linux distributions are also good, but FreeBSD will likely be more educational in the areas that count unless you decide to use Gentoo Linux, Slackware Linux or Linux From Scratch.