I'm not a designer, heck I'm hardly a writer, but I do know good software when I see it (and a cute company logo). CSSEdit is a good piece of software, and it has only gotten better with version 2, released today. But what is it, you ask? CSSEdit is the premier CSS editor (that's Cascading Style Sheets to you) for OS X. Version 2 is faster, can save CSS from a remote website better, and auto saves your work. The big ticket feature is previewing CSS for dynamic applications (think blogs).
A demo is available while a full license will cost $29.95.