Development tools
For developers, it is useful to install other additional tools.
On Mac OS X, I recommend installing XCode from Apple, MacPorts (http://www.macports.org/install.php), and then use MacPorts to install the package dos2unix ('sudo port install dos2unix').
On Linux, it is useful to have the dos2unix (or is it mac2unix) program installed. This facilitates converting back and forth between text on Mac OS 9 machines.
On Windows, I like to install cygwin so that I can use my favorite text editor (vim). When I install cygwin, I also like to install openssh, bzar, and vim.