Calendar implementation is taking a lot more time that we initially thought. We have to synchronize SharePoint calendar (one domain) with master Outlook calendar (another domain). It's not easy as it sounds. We spent 2 days googling Internet and trying to find a solution. Finally
we found something interesting and closed to our need. It's an Exchange calendar web part written by Swiss software company which specializes in Sharepoint web parts. It's quite interesting piece of software written for SharePoint. It contains several dll-files and one web part file.
We'll see if it's going to work for us... A day later I can say: IT WORKS only with right permissions between domains.