Roland TB 303 Emulator online
Now you can use a free software version of the TB-303 from your web browser.
I know it doesn’t look exactly like the original TB-303, but it has many of the same controls. You’ve got saw and square wave, tune, cutoff, resonance, envelope mod, decay, accent, octave a slide. Actually, Acid Machine is more than just one TB-303. It features two of them, plus a drum machine too!
My only criticism is that it seems like the filter cutoff and resonance don’t go as extreme as they do on the real thing. Still, it’s free, so we can’t really complain too much.
You can have a play with it right now HERE