I like to use Outlook to sync to my phone for contacts but for some reason prefer to use Google Calendar for my calendar. In the past I have used some freeware to connect my Google Calendar to Outlook but it doesn't work very well with Outlook 2007.
I don't know if it's a big seceret with Microsoft or not but they do list a way with Outlook 2007 to add your Google calendar with Outlook. It won't put it in your main calendar but you can add an internet calendar to pull in your Google events.
From the Microsoft site:
Subscribe to your Google Calendar
You can subscribe to your calendar posted on Google Calendar. An Internet Calendar Subscription keeps your Outlook copy of your Google Calendar updated. Outlook periodically checks the Google Calendar for updates, and if any are found, they are downloaded to the calendar copy in Outlook.
1. Log on to your Google Calendar account.
2. In the left column, under Calendars, click the arrow button next to the calendar that you want to add to Outlook as an Internet Calendar Subscription.
3. Select Calendar settings.
4. Under Private Address, click ICAL.
5. Select the Internet Web address that appears, and then press CTRL+C to copy the selected text to the Windows clipboard.
Note Do not click the link. If you click the link, the calendar will be opened in Outlook as a Calendar Snapshot which is not updated.
6. In Outlook, on the Tools menu, click Account Settings.
7. On the Internet Calendars tab, click New.
8. Paste the Internet Web address you copied in step 5, by pressing CTRL+V.
9. Click Add.
10. In the Folder Name box, type the name of the calendar as you want it to appear in Outlook, and then click OK.
Note To make changes to your Google calendar, you must use Google Calendar. Changes makde in Outlook are not sent to your Google Calendar.