Since my friends share their schedules with me in Google Calendar, when I want to see a movie with them, I can check to see which nights they're free before sending out an email about it. However, I need to switch between Gmail and Calendar in order to check their availability and send an email invitation.

Today, we're launching a new feature that brings tighter integration between Gmail and Calendar, making it easier to create Calendar events from within Gmail. When you compose an email message, there's now an "Insert: Invitation" link right under the subject line.

When you click it, a small window appears that displays your availability as well as that of the people you're emailing provided you have permission to see their calendars.

You can check your friends' availability and choose an appropriate time for the event you're setting up right from there. When you've settled on the details of the event, click the "Insert Invitation" button and a preview of the invitation will appear in your email message:

When you send the email, the event gets added to your calendar as well as to your friends' calendars.