Metronaut - An app to help you play classical music
Limnu - Sketch, share and collaborate with your team
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
Sketchboard.io - Visual Remote Teamwork. Solve problems and create ideas on endless whiteboard with your teammates by sketching.