WP Live CSS Editor is a new plugin that is actually a port from a Drupal module called Live CSS. It allows you to preview realtime CSS changes and then save the CSS back while keeping dated backups. You can edit any and all CSS files that are loaded in the page, provided they have write permission and you are looged in.
If you’re going to be doing a lot of CSS editing on your WordPress site, then this plugin might be just the ticket for helping you to be more efficient. Download WP Live CSS Editor for free from the WordPress plugin repository.