PHP

Minify

Minify combines multiple CSS or JavaScript files, removes unnecessary whitespace and comments, and serves them with gzip encoding and optimal client-side cache headers.

Combine

PHP script combined with URL rewriting to concatenate and compress CSS and JavaScript files.

SmartOptimizer

A PHP library that enhances your website performance by optimizing the front end using techniques such as minifying, compression, caching, concatenation and embedding. All the work is done on the fly on demand.

CSSTidy

Compression of CSS files. Note: no support for JavaScript files.

JSMin+

PHP-based and it parses the JavaScript. Note: no support for CSS files.

CSScaffold

Compresses, caches and gzips CSS on-the-fly. Note: no support for JavaScript files.

CSS-JS-Booster

Concats, minifies and gzips CSS and JavaScript files.

CSS Crush

Concats and minifies CSS files.

Django

Django Static Management

Intended as an easy way to manage multiple static text assets (CSS and Javascript) in a Django projects.

Django compressor

Compresses linked and inline javascript or CSS into a single cached file.

django-compress

django-compress provides an automated system for compressing CSS and JavaScript files. Note: Doesn't support concatenation of files..

Deploying compacted javascript with django

Management command to compatct JavaScript. Note: No support for CSS files..

Templatetag for JavaScript merging and compression

A templatetag that merges several JavaScript files (compressing its code) into only one JavaScript file. Note: No support for CSS files..

Ruby

Sprockets

Sprockets is a Ruby library that preprocesses and concatenates JavaScript source files.

Juicer

Compresses CSS and JavaScript code, JSLints it and also supports Data URI-embedding of images in CSS files.

Jammit

Jammit is providing both CSS and JavaScript concatenation and compression, 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.

AssetPackager

Merges and compresses JavaScript and CSS when running in production.

Java

YUI Compressor

The leading tool in the for compressing CSS and JavaScript files, and could easily be ported/encapsulated into other environments. Note: Doesn't support concatenation of files.. Could be used in conjunction with an Ant task, as described in Building Web Applications With Apache Ant

Google Closure Compiler

Google Compiler for JavaScript that supports various compressing options for JavaScript. Note: no support for CSS files.

Jawr

Supports concatenation and minification of CSS and JavaScript files.

Granule

Combines and compresses CSS and JavaScript files.

.Net

YUI Compressor for .Net

A .NET port of the Yahoo! UI Library's YUI Compressor Java project.

Packer for .NET

A tool to pack/minify CSS and JavaScript files.

Microsoft Ajax Minifier

A tool to concatenate and minify JavaScript files. Note: no support for CSS files.

CombineAndMinify

A tool to concatenate and minify CSS and JavaScript files.

StyleManager

A tool to concatenate and compress CSS files.