Learn a free Unix - like Linux or BSD. Really. A huge part of hacking IMHO is taking an open system that is sometimes quite complex (like an OS), shedding your fear of breaking things, and tinkering. When things do break, you will learn so much from fixing them. =) It is a lot of fun, free, and will get your feet wet with some of the other stuff that mechanical_fish mentioned.

I also recommend Emacs. I haven't worked with git just yet, but I use Mercurial all the time (and I will eventually get around to using git). Avoid CVS like the plague.