The first thing that I noticed when I saw Arduino code was that its C.
I would suggest like everyone else is saying, go and learn the basics of C while you are waiting for the board.
Beside being useful for working with Arduino learning C will help you with PHP, Java, Javascript, not to mention give you a foundation to go one C++ or C#.
C was one of the first languages I learned after BASIC. So far investing in learning C has been very good, because it has allowed me to move to so many other langauges. You can see how C has has inspired so many other programming and scripting languages. I can even see how python was inspired by C.
If you can get your hand on a book called C programming by Kerningham and Ritchie the inventors of C, you will find more than you need. Otherwise if you are very new to programming just learn the basic sytax of C which is all you need to get started with Arduino and build on that as you go along.