Microsoft SuperPreview
In late February, Matthew pointed out a few browser testing tools to help you see how your site renders in different browsers. Microsoft just announced an addition to that list: Microsoft SuperPreview. According to the post on SitePoint, the full version, which hasn't yet been released, will support Internet Explorer, Firefox, and Safari. Currently, a free pre-release version lets you test IE6 and IE7 as well as IE8 if it's installed. - K
A really nifty (and novel) feature of SuperPreview is the overlay mode, which allows you to compare one page on top of another.