I would say you should go for C++. There are simpler languages to learn; but C++ is widely used, it can be used for many things (from games to operating-system and device-drivers), and it's similar to C, C#, ObjectiveC (which I think is/was used on Mac) and Java. Mind you, this is if you want to program applications, not making script for web-pages and similar.
You should also check-out Nokia's Qt library, which makes it easy to make GUI-programs and it's RAD; Qt-designer.
Pascal is probably a better language to learn programming, as it forces you to use good methodology -- like enforcing a certain order of different parts of the program (constant-definitions, variable declaration, function definition). Delphi is a RAD based on Pascal (though AFAIK only for Windows).
Alas Pascal's popularity has dwindled, so if you want to learn just one language, learn C++. Though it *is* a good idea to learn several -- and several "types" of languages (C++ and Pascal is basically the same type) -- if you want to become a good programmer. You'll learn different techniques, and can choose the best tool (language) for the job.
RAD=Rapid Application Development. You *design* a GUI-program by interactively place the widgets (buttons, list-boxes, menus, ...) in a the different windows/dialogues the program is supposed to consist of. The RAD then provides skeletons for the different functions that should be run when actions (like a click) happens to those widgets. Most of the programming can thus be accomplished in that way. Much -- including how to stitch the parts together to one program -- is provided automatically by the RAD.
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C++ is an Object Oriented Programming Language, but sadly not a very good one. C++ is basically C with object-oriented stuff glued on top, while ObjectivePascal is Pascal with oo-stuff glued on top. C++ also lacks a comprehensive single class-hierarchy. Java is all OO, but is heavily influenced by C++. Java has a single class-hierarchy, but the primitive types (Integers, Floats, Chars) are defined outside of this. Also C# is too influenced by C++.
So to really see the beauty of Object Oriented Programming, you may want to try a language like Smalltalk. Everything -- including the language itself and all types -- are part of *one single* big class-hierarchy. It really shows how OO is supposed to work, and where half the job is to figure out the best place to insert a new class to take full advantage of it's parent-class. Programming in Smalltalk though, is very different from programming in C++.
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There are also scripting languages like Tcl with it's GUI-extension Tk (thus Tcl/Tk) and Perl which are great to make scripts for automating system administration and can also be used for programming scripts for web-servers. Python (similar to C++) and Ruby (similar to Smalltalk) can also be used for those tasks, and (at least) Python is also good to program GUI-programs -- including games. They are all great to make small scripts to get some routine work done.
LISP is yet a completely different type of language -- a list-based language, suitable for AI among other things. The Emacs-editor uses it for it's many functions and modes. Haskell and Scheme are basically the same as LISP. LOGO is a similar language, intended to learn computer-science to children (though perhaps younger than 13) and run the "turtle" -- a little robot that can draw figures on paper.
Ada was supposed to become the "universal programming language", and was for a while (still?) the required language for Government projects in the USA. It's a bit similar to Pascal. I wouldn't bother with it as a first language to learn.
Eiffel was the language introduced in a very popular book about programming, and is perhaps a very good language to *learn* programming in. Though AFAIK it's not very commonly used.
Assembly may also be useful. It's programming almost in machine-code.
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If you intend to program towards the web, learn PHP to make server-side scripts (though Perl, Python and Ruby can also be used). PHP is perfect to make database-driven sites. JavaScript is great to make interactivity on the client-side (programs run in the browser), and is used in "Dynamic HTML" (DHTML). Of course you must learn HTML/XHTML and CSS too, which is the language the actual web-pages are written in.
Java may be a bit slow, but it is often sought after by companies. It's OK for making stand-alone applications (though C++ is better), and great for making "applets" -- small programs that are downloaded from the web and becomes part of a web-page (like chat-clients or secure logins). If you plan to make web-pages, you should learn Java to supplement JavaScript.
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I would go for C++, perhaps with Qt. But maybe also look at Smalltalk to understand OOP better. Learning a scripting language -- like Perl or Python -- would also be useful to create "small stuff" in a hurry.