This is the Textmate bundle for Slim, based on the Handcrafted Haml bundle.
cd ~/Library/Application\ Support/TextMate/Bundles/
git clone git:https://github.com/fredwu/ruby-slim-tmbundle.git Ruby-Slim.tmbundle
osascript -e 'tell app "TextMate" to reload bundles'