CDN Fu is a fun domain specific language for deployment of assets to content deliver networks.
Currently the gem is on gemcutter.org, so you need to add that to your sources
$ gem install --source=http://www.gemcutter.org cdn_fu
First install the gem, then do the following $ cd your_rails_dir $ cdnfu --rails . $ rake cdn:init
Check out the CDN Fu Homepage for more details and examples