Jammit is an industrial-strength asset packaging library for Rails, providing both the CSS and JavaScript concatenation and compression that you'd expect, as well as YUI Compressor and Closure Compiler compatibility, ahead-of-time gzipping, built-in JavaScript template support, and optional Data-URI / MHTML image embedding.

Gem for splitting up stylesheets that go beyond the IE limit of 4095 selectors, for Rails 3.1+ apps using the Asset Pipeline.

Ruby on Rails plugin - CSS/JS asset bundling in 10 seconds or less!

Load CSS and JS faster. Minifies, bundles, and optimizes CSS/JS assets ahead of time (e.g., on deploy), not at runtime. Loads popular third-party JS (like jQuery, YUI, and Dojo) from localhost in development, and auto-switches to Google's CDN in production. Lets you switch on LABjs mode to load more scripts in parallel. Can rewrite stylesheets to use CDN hosts (not just your web server) and cache-busting hashes for updated images.

Rails plugin to automatically minify JS and CSS when their bundles get cached. Send in those patches!

Smart asset packaging for Rails, Sinatra, and Stasis.

Rails plugin to allow for compressing and bundling JavaScript & CSS files for production

A Railtie that provides an asset management system for css, javascript, and sprites in your Rails applications and engines. ActiveAssets includes two libraries, ActiveExpansions and ActiveSprites. ActiveSprites generates sprites defined by a dsl similar to a route definition. Similarly, ActiveExpansions' dsl creates ActionView::Helpers::AssetTagHelper javascript and stylesheet expansions, and adds additional features

rucksack is a Rails plug-in to pack and compress CSS- and JavaScript-files with the YUI Compressor. It's easy extendable to use other compressors like Packer, JSMin and CSSTidy.

Grunt-based workflow for your Rails assets

Sprocketize provides a command-line utility for the sprockets gem so it can be used without rails.

Minify for rails js and css

Raptest plumbs Rails assets pipeline detecting any issue that may come out during and after their deployment