Adobe has responded to calls from developers for better sound generation capabilities in Flash, and is introducing new features in Flash Player 10 that should lead to more sophisticated Flash based sound tools:
Dynamic Sound Generation — Dynamic sound generation extends the Sound class to play back dynamically created audio content through the use of an [...]

Nice intro video for the Hobnox Audiotool that offers an introduction to creating beats.
AudioTool is like Reason for your Web browser.

Adobe, MAKE SOME NOISE is a campaign, which addresses the lack of dynamic sound manipulation in Flash.
It’s basically a group of Flash audio hackers that are working to get Adobe to make Flash a more powerful platform for audio manipulation:
We think that Flash is and still will be the most popular browser plugin worldwide. Software [...]

This gets my vote for the coolest thing you’ll see this weekend.
It’s a live performance using the Hobnox AudioTool - the new browser-based virtual studio - using a MIDI controller and Percussa AudioCubes.
See the tutorial at the Hobnox site, too!
Joa Ebert & Kai-Phillip, via David

If you check out one thing this weekend, check out Hobnox AudioTool.
It’s like Reason for your Web browser - a collection of Web-based audio tools that you can patch together in play, including a TB303, TR808, TR909 and a variety of effects pedals.
It’s just a demo, but I’m impressed. Let me know what you think!