Google+ is the talk of the week. Everyone has a G+ account, but just not your friends. You want to invite them all, but Google says email invitations are currently not available. Don’t worry, There is a work around for this.
P.S: You can also ask your friends who have a G+ account to do this to receive an invite.
- Log in into your G+ account
- Post something on your stream in your home tab.
- Share the post with your friends in your circle by clicking on
Share this postbutton which is present below the post. While sharing make sure that you select “Also email people not yet using Google+“. Here, you can also type the email ID of your friends whom you wish to invite here. - Tada.. All your friends will receive an email invite instantly.

It is working perfectly as on 1st of July-2011. And there is no limit in sending an invite, at-least as of now.
Thanks to Aron for this tip.
July 1, 2011