Quick tip that I found when searching to find out how to get syntax highlighting in your Gemfile if you are using TextMate Ruby on Rails bundle.
In Textmate, select the Bundles menu => Bundles editor
Select languages instead of show all.
Select the Ruby on Rails language within the Ruby on rails bundle
Change this line:fileTypes = ( 'rb', 'rxml', 'builder' );
to this:fileTypes = ( 'rb', 'rxml', 'builder', 'Gemfile' );
Go to Bundles => Bundles Editior => Reload Bundles.
Reopen your Gemfile and you should now be getting the syntax highlighting.