Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
Palaround - Meet people you should be friends with.
Pushbullet - Pushbullet - Your devices working better together
Digg - Digg delivers the most interesting and talked-about stories on the Web right now.
Gotify - a simple self-hosted server for sending and receiving messages
quippd - quippd is a social news site that anyone can edit.