If you're using edge rails you may have noticed that you can now define your own JavaScript expansions (if you're not on edge this will be included in the imminent 2.1 release). The default expansion that comes with rails looks like this:

javascript_include_tag :defaults

Which grabs application.js as well as the prototype/scriptaculous javascripts and includes them all (only do that if you need it all - it adds ~150kb to your page). But say you've got a line which looks like this:

javascript_include_tag 'my_js_file', 'another_js_file', 'and_another'

And say you want to include the same set of files on a different page - it turns out Rails makes it really easy to DRY this up. Make a new file in the config/initializers directory (I call my asset_tag_expansions.rb) and add a line like the following (don't forget to restart your server afterwards):