Mark Russinovich created a utility called PsExec that allows you to run programs as a limited user. A little work and you'll be running both Internet Explorer and Outlook in a mode that would severely limit the vulnerabilities in each of these applications. Unfortunately, it requires a little bit of technical knowledge to setup. I'm hoping Mark will allow me (I sent him an email) to create an installer that'll make the setup a little easier.

http://www.sysinternals.com/blog/2006/03/running-as-limited-user-easy-way.html