I found this really slick utility through Digital Media Minute. CSSVista (a free application, Windows only folks) allows you to edt your CSS live in both IE and Firefox... (wait for it...) at the same time. It opens a copy of your page in IE and Firefox in a split view window. You can then edit the CSS just like you would in Firefox and your changes are immediately displayed in both browsers.

This is going to save me a ton of time... I often debug my CSS in Firefox, make sure it's all working, then copy the CSS to Dreamweaver and start testing in IE. Now I can do it all in one place.