Google Calendar Sync
This nifty freebie from Google is designed for a problem that bedevils many who use Google Calendar as well as Microsoft's Outlook calendar--how can you keep them in synch? If, for example, you use Outlook for your personal calendar, and Google Calendar for your work calendar, you have to manually retype all of your appointments.
Google Calendar Sync solves the problem neatly. It automatically synchronizes events in your calendars. So just enter them once, and they show up in both places. You also have the choice of synching events only from your Google Calendar to Outlook, and vice versa. So, for example, if you use Outlook for personal events, and don't want to share them with co-workers, but you do want all Google Calendar events in your Outlook calendar, you can do that.
There's only one annoying thing about this freebie: Google Calendar Sync will only synch your primary calendar, not any secondary ones. Worse yet, Google Calendar offers no way to change your primary and secondary calendars, so you're stuck with synching your current primary calendar.
Note: This download takes you to the Google Calendar Sync page, where you can download the file.