Allo.io - Whiteboarding, documentation, and video chat in one place.
Metronaut - An app to help you play classical music
Butter - Butter is a newly launched chatting application that focuses more on the privacy of its users.
Flat for Education - The best way to teach music to your students
Draw.Chat - Anonymous real-time whiteboard with text and video chat.
Scribd Sheet Music - All the sheet music, books and comics you want for $9/month