I meant to blog about this last year when I discovered it, but this appears to be the little-known Holy Grail of syncing applications. SyncMyCal is an Outlook plugin that synchronises your Google Calendar with your Outlook calendar – and both ways too!
If you search for “Google Calendar sync” you’ll find lots of people searching for the perfect tool to get two-way syncing happening between Google Calendar and Outlook. SyncMyCal comes in two versions, both versions provide full, two-way syncing, but the limitation on the free version is that you can only sync a range of 7 days of items, whereas the full version ($25) allows unlimited syncing.
This definitely works, although I have only used the free version so far. I was reminded of the tool after reading Jon Udell’s blog where he outlines the difficulty in getting multiple calendars synced.