Environment: SharePoint 2007 – wss or MOSS (no SharePoint Designer or third party application required).
Audience: confirmed end user, power user.
Permission level: design or full control.
Estimated time: 15 minutes.
Christophe is the man. I have this solution running on two team calendars on my farm. Works like a charm, though perhaps it speaks to the level of real SharePoint readiness of any stakeholder who asks for it. I mean Outlook can do this, and roll up at the same time.