ericmc

I also recommend Computer Systems: A Programmer's Perspective to anyone who wants an intro to systems. One of the best textbooks I've read.

Most likely Textmate with the railscasts theme (http://railscasts.com/about).

I've used this before to change the colors and it works well: http://ciaranwal.sh/2007/11/01/customising-colours-in-leopar...

While TextMate is nice, and I paid for it myself, I recently decided to start learning Vim because you can essentially use it on any platform. It may take some time to learn, but I believe it will be greatly beneficial in the long run.

I urge you to check out MacVim (http://code.google.com/p/macvim/).

You can add many of TextMate's features to Vim using plugins like snippetsEmu.