I was unaware of this until recently so you might find it useful.
You can create a list of all your favorite rails plugins at Agilewebdevelopment.com and use RaPT to install the entire list into a newly created rails app.
To install RaPT:
sudo gem install rapt
Go to agilewebdevelopment.com, login and add plugins to your favorites. The site will provide you with a unique url that you can use to install the pack of plugins.
rapt pack:install http://agilewebdevelopment.com/favorites/ pack/243610d6bf75
Enjoy.