Myna, a free online audio tool from the makers of reader favourite image editor Phoenix, lets pretty much anyone jump into recording, arranging, and mixing audio tracks for quickie soundtracks, or just for the fun of it.
Myna's horizontal track-over-track layout should be familiar to users of audio tools like CoolEdit or FruityLoops, but it's pretty easy to pick up on, too. Hit the Snap to Grid button, set your beats per minute, and arranging audio clips from your own files, from a microphone, or Myna's sample libraries is just a matter of putting the pieces in place. Poke around some more, and you'll find tools for volume adjustment, gain control, reverb and flanger effects, and a few other neat effects. It's not quite a multi-track Audacity, but for something you open free in your browser, you'll probably be seriously impressed at how much Myna has to offer.
Here's a video walkthrough and track construction sample from the Myna team:
And here's what I was able to whip up after about 30 minutes of messing around with Myna. The nasal-voiced rant about Chrome's tab closing is from my headset, while the background tunes are from Myna's sample track and loop libraries:
Myna is a free service, requires a user account to save a "mixdown" of a track, which you can then download and embed freely. Share your own Myna creations, and recommend other free audio tools, in the comments.