These formulae provide x11 apps.
How do I install these formulae?
brew tap homebrew/x11 and then
brew install <formula>.
If the formula conflicts with one from mxcl/master or another tap, you can
brew install homebrew/x11/<formula>.
You can also install via URL:
brew install https://raw.github.com/Homebrew/homebrew-x11/master/<formula>.rb
man brew, or the Homebrew wiki.