Google Music Lab - Interactive experiments that use the Web Audio API
Youtube-DJ - Mix YouTube songs together
Splice Beat Maker - Make and share beats in your browser
Edjing - Discover edjing and edjing Pro, the most powerful DJ apps for music lovers! Mix on Android, Windows and iOS devices and record then share your DJ sets!
108 - A minimal beat machine played in the browser.
YOU.DJ - Mix SoundCloud music and Youtube videos live in your browser.