The great Bart Bultinck informed me of this great Outlook plugin (for Outlook 2003 & 2007) while it was still in beta. Back then, it worked only with invites (like gmail a couple of years ago), but now everyone can download and use it for free.
Read about it on the NY Times Website or just go to their website, http://www.xobni.com. It's fucking awesome, I use it constantly...
Keep on emailing