GroupMe
GroupMe is a mobile group messaging app owned by Microsoft. It was launched in May 2010 by the private company GroupMe. In August 2011, GroupMe delivered over 100 million messages each month and by June 2012, that number jumped to 550 million. In 2013, GroupMe had over 12 million registered users.
Your can use GroupMe on your desktop computer with All-in-One Messenger.