Textmate is a modern editor for OS X. textmate-clojure is a textmate bundle providing syntax highlighting and clojure integration through cake.
cd ~/Library/Application\ Support/TextMate/Bundles
git clone git://github.com/swannodette/textmate-clojure.git Clojure.tmbundle
osascript -e 'tell app "TextMate" to reload bundles'
gem install cake
For more information and a list of commands, see the README