As there are some bad apps to share, there are also good ones. Good apps to share means they share no personal information, such as a picture of you, your full name, your adress, etc. Some of the "OK" apps include:
Google Docs is a great way to communicate with other Hopscotchers! You can chat about games in private (such as your doing a collab and you don't want anyone else to know the information), write books, and more! Many people use it, including the @admins and myself to communicate! Just make sure if you use the application, use an email that doesn't reveal you full name or a picture of yourself!
Thats all I have (for now)! Any more ideas?