Google Calendar provides a great way to store you calendar online so it can be access form any computer with an internet connection, or even a mobile phone or PDA. While the online calendar is undoubtedly useful, it does lack some of the features of a dedicated PIM such as Outlook.
SyncMyCal is a calendar synchronisation tool which can be used to synchronise data between Google Calendar and your Outlook calendar. Two way synchronisation means that either calendar can be used to create or delete appointments and the changes, additions and deletions will be reflected in the other.
If your Google Calendar is shared you can opt not to synchronise Outlook events that have been marked as private and it can be used to synchronise multiple calendars. Automatic schedule adjustment adds support for different time zones and appointment categories can also be synchronised. Whether you just want to keep your own calendar up to date or want to ensure that users of a share calendar can update events from anywhere, this may be the tool you have been looking for.
The Pro version of SyncMyCal also feature automatic synchronisation and can be used to synchronise any range of dates rather than just 7 days. This version will also synchronise contacts.