I've found myself creating a number of new Rails apps as of late, and found it very cumbersome to set each one up with my favoured list of gems and plugins. So I created my own Rails Template.
Rails templates are single ruby scripts which contain a few commands that help you setup any new Rails app in a snap. So you can specify a list of Gems to have installed and part of your environment.rb, and also install a bunch of plugins, amongst other things.
You should take a look at Pratik Naik's blog post for full details on what Rails templates can do.
So my default Rails template is called Railings, and is available now on Codaset. It is sure to grow by the day, but for now, this is what you get:
So the next time you start a new rails app, run this command and you will have the world at your fingertips:
rails -m http://codaset.com/joelmoss/railings/source/master/raw/railings.rb /path/to/mynewapp