Google has added a couple of useful features to Gmail which are now available directly on the main client without them having to graduate from Labs. The first is based on HTML 5 and will allow users to comes in the form of a little "insert invitation" link just at the bottom of the subject line of outgoing e-mails. When clicked, it opens a Google Calendar invitation-maker that includes a visual of when there are open times to meet based the invitees' schedules (provided you have access to view their Google Calendars).