I use Topstyle. A "lite" copy of this came with the version of Homesite I use, but I also have version 2.51 installed over it (which I got for free off a magazine CD). There are a number of free and freeware (I'm very keen on freeware) CSS editors out there. The ones I found after a simple search were (details added where I've used them)...

Amaya (free W3C's Editor/Browser) http://www.w3.org/Amaya/
This is an odd combination of browser and editor, which runs a bit slow. It's open source however, and if it works under Amaya, then it's probably "official". I haven't actually used the CSS component, but apparently it's there.

Style Assistant (freeware)
http://www.styleassistant.de/
Not sure what to make of this. The website is in German which I don't speak, and the interface looks very forced.

WebAttack Freeware (Cascade DTP, Balthisar Cascade, xStyle)
http://www.webattack.com/
Web Attack's collection of Freeware Style Editors.

Other Stuff

Style Master CSS Tutorial http://www.westciv.com/style_master/academy/css_tutorial/
Stylemaster is a commercial CSS editor. I have a free previous version which came from a magazine CD, but prefer Topstyle 2.51 instead (also from a mag CD).

W3Schools CSS Tutorial
http://www.w3schools.com/css/default.asp

Javascript Kit DHTML/CSS tutorials
http://javascriptkit.com/dhtmltutors/index.shtml

Edited by: RobM on 18-Jul-2018 14:04
Removed Morphon, Causeway, Topstyle Lite as all are dead links; WebAttack link dead but the site is active