A Sublime Text 2 syntax definition file to offer syntax coloring for your .gitignore files. It may work with TextMate also, but I haven't tested it.
Go to the "Packages" directory (Preferences / Browse Packages...). Then clone this repository:
git clone git://github.com/lifted-studios/Gitignore.tmLanguage
Once installed, you can open any file and select the Gitignore syntax from the syntax picker in the status bar or it should be selected automatically when you open a file named .gitignore.
Source: https://github.com/lifted-studios/Gitignore.tmLanguage
Authors: Lee Dohm, Lifted Studios