Bamboo Nation offers a way to display multiple Exchange calendars in a SharePoint:

“One of the coolest things we have ever created is the ability to view multiple Exchange user calendars overlaid on one another in a single view in the Team Calendar Web Part. This makes it a true, collaborative, team calendar. So often you hear words like ‘collaboration’ and ‘team’ when talking about SharePoint products, but when you look at them closer, you find out that it is not really collaborative at all and requires a lot of work and process improvement to get it to a point where it might be just scratching the surface of collaborative. But with this new functionality, the Team Calendar Web Part really earns its name. “

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