Apple have announced an extension to their .Mac service, and they have rebranded it as "Mobile Me". The initial information available at their web pages at http://www.apple.com/uk/mobileme promises seamless integration with Mac and PC. They particularly claim that Mobile Me calendar will synchronize with Outlook and iCal and will provide push updates across all the computers connected to the account.
Imagine the following scenario: you run Microsoft Outlook on Parallels or on a dedicated computer at work. Outlook synchronizes your Exchange calendar to Mobile Me, and your iCal also works through that service.
Given that Mobile Me is developed by Apple, I'd imagine that it would actually work and be more secure than using some third party synchronization proxies from companies I have never heard about.
Unfortunately, they are not rolling Mobile Me just yet, but please come back after they have, and I'll tell you if it worked for me.
Any speculations on whether it is going to work or not?