In a good way! I just found this extension to Thunderbird (my preferred mail client):
From the project home:
Lightning brings the Sunbird calendar to the popular email client, Mozilla Thunderbird. Since it's an extension, Lightning is tightly integrated with Thunderbird, allowing it to easily perform email-related calendaring tasks.
I haven't had the best luck with Sunbird in the past, but Lightning works REALLY well! I can import my appointments from LookOut, er, OutLook, and can also view my Google Calendar in one interface that I always have open!
I voted for an RFE to make the calendar panes dockable, so I hope that feature gets incorporated soon. It's a terrific little extension, so I encourage you to check it out!