TextMate 2.0 alpha is avaialable for free download here: http://macromates.com/download
Sublime costs money, and TextMate is good enough!
All of the syntax highlighting and power of TextMate comes from bundles for supporting various languages. What you are looking for is a ".tmbundle" extension.
My bundles are located in two places. For bundles that come preinstalled with TextMate:
~/Library/Application Support/TextMate/Managed/Bundles
3rd party bundles I installed myself are in:
~/Library/Application Support/Avian/Bundles
To install a bundle, find it on github, and navigate to your 3rd party bundle folder. Then simply:
$ git clone git://github.com/REPOSITORY.git BUNDLE_NAME.tmbundle
The BUNDLE_NAME does not matter, and usually the author of the bundle will make a suggestion.