Squishify was created out of the need of a minifier for JavaScript. I quickly put together a web-app on AppHarbor to make minification always available quickly. The code is hosted on GitHub.
The application is an ASP.NET MVC-app, using Justin Etheredge's framework for minification called SquishIt. The app also uses ASP.NET Web API together with some simple jQuery to display the results of the minifications without any page-reloads.
The SquishIt-framework is a very easy to use and provides multiple minifiers for both JavaScript and CSS.
JavaScript minifiers:
* At the moment of writing this post, Google Closure is not working as expected, but should hopefully work soon.
CSS minifiers:
Enjoy it at squishify.apphb.com and fork it on GitHub.