Xc2iCal is a program, which reads your cached Microsoft Exchange (IMAP) account, extracts the calendar data and represents the result as a calendar subscription in iCal.app.
If your subscribing your Exchange account via IMAP or the Exchange dialog to you Mail.app on Mac OS X (tested with Leopard), Mail.app is caching all your folders on the Exchange server.
My program (CalServer.app) reads exactly this cached data from your mailbox cache, generates an iCal calendar and works as a small web server presenting this iCal calendar for subscription to iCal.app
All you need are to small programs included in the disk image:
Copy this two programs to /Applications/Utilities for example.
Set up your Mail Account with Mail.app to your Microsoft Exchange Account
This program shows you the configuration file in TextEdit.app
Edit the file as mentioned in the comments. You will need the following data:
Your Calendar folder name (you will see it as folder in Mail.app)
Your profile-cache folder (located in ~/Library/Mail/...)
An unused TCP port on your workstation (like 8888, which is normally not used)
Save your configuration and close TextEdit.app
Start CalServer.app (you can put CalServer.app in your Startup items. It will finish immediately, let only the server part running. It has no Dock Icon!
Open iCal.app and subscribe to the following calendar: http://127.0.0.1:8888/ (or another selected port from the config file above)
Finish! Now you will see your Microsoft Exchange Calendar read only.