As any Mac user who deals with Microsoft Exchange invites will tell you, Exchange screws up the time zone information. What this means is that you will likely miss your meetings. Not a good thing. I've adapted an AppleScript from an older hint to correct this problem. This script can either run from the System-wide Script menu from within Mail.app, or as a Mail.app rule.
Here's my modified script. Save the script and either set it up to run from a Mail rule, or as I do, call it from the system-wide AppleScript menu. You will need to save the script in ~/Library » Scripts » Applications » Mail/ folder; create this folder if it doesn't exist. This solution has the advantage of being a single script with a simple user modification for customization.
There is one property at the head of the script that needs to be modified. It is the iCal-approved location of your Exchange server. What you need to do is copy in the correct property from what iCal expects to see as time zone information. You can find this information by selecting the Time Zone drop-down menu in the upper right corner of your iCal window and selecting Other. Once there, find the location of your Exchange server and see what the resultant time zone information looks like in iCal. In my case, I live in California and my time zone is US/Pacific or America/Los_Angeles, but the Exchange server in question lives in Dallas. So I set the property to US/Central.
I think I've built in the enough logic to grab any twisted time zone information out of the Exchange invite that Exchange can produce. And with the correct time zone information listed in the script's property, a correct iCal invite will be created and processed. If I'm wrong, let me know. You can read more about this script on my blog.
[robg adds: I haven't tested this one.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080505152534523