Ies4osx is a free application that run IE 4 – 7 on your Intel Mac. Using the Darwine version of the Wine Win32 API translation layer, the app installs an official version of IE on our Mac, and it runs through X11.
According to TUAW the browser almost looks like some sort of bizarro version of IE, but runs well, and could be useful for checking code to make sure that your website will look right Microsoft’s browser.
Don’t, however, expect to be able to run things like Netflix’s Watch Instantly feature, or things like that in the browser, because they’re not going to work without Windows. In fact a lot of IE’s functions won’t run without Windows, so if you need them, I’d recommend going the VM Ware or Parallels route.