Most of my calendar data lives in Outlook. Not by choice, mind you, but because that's just where it has accumulated over the years.
I'd rather use Google Calendar, which is more versatile and less, well, Outlooky. Just one problem: how do I move my data from the latter to the former? And, just as important, how can I keep the two entities in sync?
Surprisingly few people know that Google itself offers a solution: the aptly named Google Calendar Sync. This free utility runs under Windows and automatically keeps Google Calendar and your Outlook calendar in sync.
That means you can enter an appointment in one spot and it'll auto-magically appear in the other--and vice versa. But you also have the option of sticking with a one-way sync, like copying all your Outlook appointments to GCal but not copying GCal appointments to Outlook.
Google Calendar Sync is compatible with Windows XP and Vista (though in my experience it works fine with Windows 7 as well). It requires Outlook 2003 or 2007--I'm not sure if it's compatible with Outlook 2010. (If you've tried it, leave a comment.)
Setup is a snap: download and run the utility, enter your Google account info, choose your sync option (1-way or 2-way), and then specify how often the utility should sync your calendars (the default is every two hours).
That's it! The first sync takes a couple minutes; after that, it's virtually instantaneous. Now you can use both calendars however you see fit, all the while keeping both in sync.