PHP
The only reason you would ever use the PHP programming language is for web development. I most situations involving the internet, you'll have no choice... this is also not an easy to master programming language. You can't even be proficient in it without learning MySQL and HTML. There are even more things to know, like javascript, if you want to make a really fancy website. I highly recommend this as a starting language to learn, but there are a lot of web developers that just can't grasp the concepts behind C and C++ after learning such a simple way of programming.
C
Not to be confused with C++, C does not have object orientation. Open source applications made in C are much easier to understand and it's choice for open source developers. It is just as powerful as C++. Secretly you do not really need the wrappers for object orientation. C is commonly faster than C++ and also it is normally used only when you have large numbers to crunch. Mathematical computations that really need the resources would be the only thing you would need to go to C for, such as an MMORPG with high end 3D graphics. Downsides include having to compile on every OS you want your program to run on.
C++
Same comments as C, but I don't like the object orientation personally. You will run across a lot of APIs that do not have good documentation and are not open source. It has irked me so much when I came across undocumented APIs.
C#
This is a great programming language on the same level of java, but if you really look into it and understand how it works, you will realize java is what C# wants to be. The standards and syntax are easy to follow, but if you ever plan to do anything cross platform compatible, be weary. C# currently has mono which allows Linux and Mac OS X users to use C# applications written with GTK, but never trust Microsoft, they really want to ruin anything that allows other operating systems to function in synchronous.
Anything .NET
.NET framework was great to the extent that it allowed developers to make, but it is only a microsoft friendly idea. Microsoft does not support open source development, they only support Microsoft development so they can say "Hey! We have everything!"
Visual Basic (Previous to v6/v6/.NET)
Visual Basic was great. The syntax is quite familiar to basic users. The downside to visual basic is the fact is is "visual" and proprietary to windows. Sure, you can WINE most of the stuff preceding .NET, but it doesn't change the fact that it is not cross platform compatible by default.
Assembly
This is the closest you can get to making logic gates on a circuit board as possible. There are various reasons you're probably not going to use assembly. The key one being the deep understanding that it requires just to make a conditional statement. The second reason is that it takes a lot of code to do the little work you need it to do. That being said, it's a great language, but I wont even go there.
Java
Developed by Sun Microsystems, java has fully open source interpreters and APIs. You can make anything in java, just don't dream of using it for mathematical operations that require heavy processor usage, like a 3D API. You would want to make an API binding for it in C. With the netbeans IDE, you get just as much functionality as Visual Basic or any Microsoft Visual Programming tool. I have had some of the greatest experiences ever with java, personally. You get full cross-platform compatibility with java, because there will always be a version of the java interpreter compiled for every operating system you would need. It is extremely powerful, I have seen x86 emulators made in java.
Python
It's free, open source, and such. I don't know much about it, but I have used it. I wouldn't rely on it for GUI applications, but I have seen wonderful stuff programmed in it. I wouldn't rely on it for anything more than I would rely on java for. If you want to learn it, get a copy of the interpreter from http://www.python.org/download/. It is cross-platform compatible and easy to learn as well. The downside is that you can compile your source to a byte code, but you might as well license anything you create as "open source".
There are other programming languages out there, but I'm just not going to cover them. These are the biggest programming languages you'll have to deal with these days. Now for some information on getting started. I am only going to get you started in C++, Java, and Python.
Getting Started In C++
Get a copy of DevCpp (go to binaries folder and download a version) for windows or if you're in linux, get a copy of g++ from your repository. DevCpp is straight forward to use. If you're using G++, you have to type in terminal "g++ sourcefilename.cpp". There are standards of programming in C++, which are dictated by ANSI or something like that. You can learn about C++ at CPlusPlus.com. Their tutorials follow the ANSI standards.
Getting Started In Java
You are in luck here! Not only do I have a great book for getting started, but I'll even explain the compiling process as well as a simple example of how to login to neopets (attached below as Neus-Lite.zip)! What you're going to do is simply compile and run the example. You need to first download the java development environment. Go here, get and install it. Now open command line, terminal, or whatever your OS calls it. Use the command cd like so: "cd path/to/directory/of/neus-lite/" (in windows you might need C:/ in front of it). After you change directory to the directory of the example, type in "javac login.java httpWrapper.java" or "javac *.java" the asterisk is a wild card meaning it can be anything. The command will compile the login example. To run the example, type in the command "java login". Even though the filename is login.class, java kinda just uses all the class files as if they were just extending the java executable. Anyways, no need for technical stuff. That is what it takes to get started in java. Now to learn java, go download the "How to think like a computer scientist, Java Edition" from here and read it in a PDF reader.
Neus-Lite.zip 3.96KB 6 downloads
Getting Started in Python
Get a copy of the interpreter from the python website and a copy of the "How to think like a computer scientist, Java Edition" e-book from here. I do not feel like going through the technical knowledge of how to use it, but I guess I will. Make a file labeled "file.py" and write the hello world example from the book into the file. In windows, open it with the python interpreter. In other operating systems go to terminal and change the directory to where your file is and type "python file.py" It has been forever since I done this, so I can't guarantee the accuracy of this information. Though I can promise the python interpreter and book are sound.
Anyways, concluding my post, I end with "have fun folks".