klaep - music collaboration - klaep is a social music collaboration network for musicians
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Madsounds - It’s like Discover Weekly, but daily.
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.
MisterJack - Make and share playlists
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.