Backfire : Save css changes made in firebug
blog.handcraft.com
blog.handcraft.com
I like to mess around in my CSS loads, trying different combinations, trying whether a property has an actual effect on the appearance/flow of the page, etc.
I like to then make changes that have been throughly tested inside vim, :w, CMD-TAB, CMD-SHIFT-R.
By separating experimentation and editing, I know exactly what is added to my CSS, without having to think about whether or not all in-browser changes are truly necessary for my purpose. I bet use of these kinds of extensions by inexperienced web-designers (togglers we might call them) will lead to extremely ugly and bloated stylesheets.
define problem -> solve problem -> refine solution -> commit/save changes.
might sounds slow, but really isn't, and keeps things clean.
Check Paul Irish's Chrome Dev Tools talk from JSConf 2011 for that and other tips.
(edit: around the 8:30 mark)
The up side: You can immediately use it with any of your sites. No setting up required. The down side: It works on top of your existing CSS and you'll still need to copy/paste the CSS into your live version.