I discovered winetricks today. This handly little script and set of tools allows one to easily install IE8 in Ubuntu. Here are the details:
Basically, once you've downloaded the script, run sh winetricks and then install the Windows component from the default wine config. After that, if you'd like a shortcut, you'll need to create a link to the iexplore.exe file in the c:\program files\internet explorer folder of your wine instance.