Devin Walker has an excellent blog post on a strictly browser-based method of moving SharePoint lists from one site to another using the List Template method. I used the instructions with success on one of our calendars.
I was concerned about the effect the move might have on events emailed to the calendar and on its display in Outlook as another user’s Calendar. These problems were resolved by giving the new calendar the same email address as the old calendar. However, making this email assignment required a direct edit in Active Directory, because attempting to assign the old address to the new calendar resulted in an error that the email address was already in use. Disabling email in the old calendar did not remove the Contact entry in AD; neither did deleting the old calendar from the site. After removing the Contact from AD directly, I was able to assign the email address to the new calendar.
Testing showed the new calendar accepting emailed calendar items, and the new calendar displayed in Outlook correctly without having to delete and re-add the new calendar as another User’s Calendar.