Keeping up with your Calendars: Everything in One Place
Managing your sharing settings
Google Calendar allows you to make a calendar public or share it with specific people. Unique permission settings can be designated for each person. The most basic setting only allows others to view when you are free or busy, blocking out the times when you have events scheduled. You can also allow other users to view all events or edit events. If you want to share ownership of a calendar, others can be invited to make changes and manage a calendar's sharing settings.
You can also view which calendars have been associated with you in the past by navigating to "Calendar Settings" through the settings icon in the upper right-hand corner of the Google toolbar and selecting the "calendars" link.
Requesting access to another calendar
If you would like to view the calendar of a colleague, friend or family member, add their email address to the "Add a Friend's Calendar" box below "Other Calendars" on the Google Calendar homepage. Selecting the "Add" drop-down link below will also allow you to browse and display other interesting calendars that include national holidays or other notable dates.
Viewing your Google calendar in Gmail
Google Gmail currently includes a Labs tool that allows you to view your calendar in your inbox, making it even easier to view your events and emails at the same time.
To implement this feature, navigate to your Gmail settings. (The fastest way to access your settings is by selecting the icon in the upper right-hand corner of the Gmail screen.) Choose the "Labs" link toward the right and search for "calendar." Enabling the "Google Calendar gadget" under the available labs will add a calendar box to the left pane of your Gmail.
These steps should mean you now know how to share multiple calendars in Google Gmail, but if you have any problems at all then please leave me a note in the comments section below.