Getting 'real' IE on the Mac, up until now, has meant OS emulation (Virtual PC), virtualization (Parallels/VMware), API translation (Wine/CrossOver) or remote access (RDC). Now there's another option for Intel Mac owners: ies4osx, a Mac port of the ies4linux package. Built on top of the Darwine version of the Wine Win32 API translation layer, ies4osx downloads and installs an official version of IE (you pick from v5, 5.5, 6 or 7) and then runs it inside the X11 environment on your Mac.
The resulting browser looks a little weird -- almost like a Bizarro version of IE, with the slightly altered type and menu look of the X11 windowing system -- but this bear can dance. OWA runs nicely, with full rich-text editing and message search, and the administration pages for MS Virtual Server also work pretty well. I wouldn't depend on ies4osx in a production role, at least not with the current build, but for one-off testing of websites in IE it's worth the (free) download. The ies4linux developer plans to roll the Mac-specific fixes back into the main package, so the next version of ies4 will probably support both Mac and Linux users from the same codebase.