If you ever wanted to simplify your deployment from development assets to production assets in Fuel PHP... Here is the best way I know.
This package leverages the awesome Jammit gem from http://documentcloud.github.com/jammit/ for javascript minification and concatenation, css minification and concatenation, compiling javascript templates, and encoding images into datauri which will drastically reduce requests and is much simpler than spriting.
It basically has two modes, production and non production. In production mode the assets.yml groups are parsed and the optimized assets are loaded. In non production mode, all assets are loaded from the assets.yml file and images are datauri encoded.
Currently the only major drawback for some is it only supports underscore's javascript templating in non production mode. I could implement this in the future or someone could do a pull request and add additional templating as needed.
The Fuel Jammit package is located at https://github.com/keith-loy/fuel-jammit and usage is explained in README.
The jammit gem provides routing functionality for Rails.
The package does not do anything specific to routing. However, all that is needed is a rewrite rule for whichever directory you would like to place your assets in so that it works properly with Fuel's routing system.
Here's how my rewrite looks in my apache vhost config...
RewriteEngine on
RewriteCond $1 !^(index\.php|assets|robots\.txt|production|favicon\.ico)
RewriteRule ^(.*)$ /index.php/$1 [L]