I needed to retrieve some HTML from another site, and feed that into WordPress. Found this little gem -- the PHP Simple HTML DOM Parser by S.C. Chen. It's an HTML DOM parser written in PHP5, which lets you find and modify tags on an HTML page with selectors just like jQuery.
Complete manual here (the link is not too obvious on the homepage).
This is the easiest way I have found, to search and mogrify foreign site's content into something useful. Highly recommended.
Blue Griffon seems to be the descendant of the moribund NVU and Kompozer projects, offering a What you see is what you get (WYSIWYG) HTML editing environment. Worth a look.
Firebug 1.6, the plugin for Firefox, is newly released; for debugging or developing web apps, like Wordpress, it is simply indispensable.
A few of my favorite features:
Scrollable breadcrumbs, solves the one biggest thing that always drove me nuts, in dealing with Real World css.
Copy CSS from the inspection window by right-clicking on the declaration:
