Open Source CSS Editing & Hosting Service: WebPutty
WebPutty is an application that enables us to write CSS code with an online, feature-rich, syntax-highlighted editor and see the changes in real-time with a side-by-side preview panel.
The CSS file is hosted by the service so that any changes made are instantly reflected to the live website. And, you can host any number of CSS files under a single account.
WebPutty was a free hosted service and it is now open sourced so that anyone can create their own instances and edit/manage CSS files of multiple projects from a single location.