Here's something to entertain you (and annoy your colleagues) on a Friday afternoon: a web-based, SID synthesis-emulating Commodore 64 synth that you can play in your web browser.
Billed as a Chrome experiment that's based on the WebAudio API, WebSID features dual keyboards and can be be played with your mouse, QWERTY keyboard or (if you have one) touchscreen. It's polyphonic, and chords played on the upper keyboard are automatically arpeggiated. You get a filter, an envelope and an echo effect to tweak.
(Via Create Digital Music)