The choice of HTML Editors his highly personal I know. But at the risk of starting a war, I’d like to recommend HyperEdit.
It offers a two paned view of your document with an HTML edit pane and a live preview (using WebKit). Granted, many text editor will do this now (BBEdit, SubEthaEdit, Taco), and I’ve tried them all, but what I really like is how light weight HyperEdit is. It opens almost instantly, and is snappy, snappy, snappy! It works well with CSS, and since my HTML is usually fairly small (most of the layout is in CSS) it is almost the perfect tool for me.
The latest beta includes a Code Snippet drawer that makes HyperEdit go from cool to the bees knees in my book. It’s nagware (but not annoyingly so) and well worth the US$10 requested.
I give it two nostrils up!
While I’m at it I might as well put in a plug for CSSEdit too. Have I ever mentioned how much I love CSS? I would never profess to be a designer, but from a strictly nuts and bolts perspective, it makes maintaining/changing the look of a web site a breeze