WPMU DEV Invite

Description

Invite allows you to invite friends and colleagues to your website to view it or join.
Marketing machine
Give your real fans a way to spread the word about your website. Make your users a powerful marketing tool.
It is easy to integrate Invite with other systems because it has a solid code base. Create a contacts exporter for web-based services such as Hotmail, Yahoo and Gmail. Then use Invite to send an email to every contact from your address book.
Edublogs has been tested and approved
Encourage your users to invite friends. Send invitations easily using the simple Email Invite form, which allows you to include a personal note with your invitation.