Google Calendar, is now integrated with gmail. When you compose a message you will see a link on the right side of the screen “Add Event Info”. This link will allow you to enter details of the event that you are inviting the recipient to. When the recipient receives the email it will appear as an invitation with options to attend, might attend, or will not attend. If they decide to attend the event, then the event will be added to their calendar.
What? if you don’t add the event information into the email directly, don’t worry! Gmail will still offer the option for the user to add it to their calendar after it finds a date in the message body, but you will not be able to keep track of the attendance.
Further more, there is “Links Bar” in the upper-left corner of the screen with direct links to the Google Calendar, Google Homepage, and Gmail.