This is my new favorite feature of Outlook 2007 Calendars. We are heavy users of SharePoint calendars and we link these to Outlook 2007. We also share all of our calendars. I can have as many as 5 or 6 calendars in a single view - too many to be able see anything of any value.
In Outlook 2007, you can overlay the calendars. When in the calendar view, click the little arrow at the top of each calendar to overlay the calendar. When you choose the tab at the top, that calendar comes into view.Too simple and I never knew it was there. Your calendars are now laid out on top of one another and based on which 'tab' is bold, that calendar's items are brought into focus.