Jonas Norberg has released PWMDrive, so called since it can produce sounds similar to a pulse-width-modulated square wave. It features "non-symmetrical" distortion and (optional) 8x oversampling - meant to be used at mixdown-time, since it's rather expensive.

The steps performed are:

1. Measure the amplitude.
2. DC-Offset signal depending on amplitude (LFO controlled).
3. Gain.
4. SoftClip.
5. HiPass (to remove DC).
6. Gain.

PWMDrive is freeware, uses the hosts default GUI and is available as a VST effect for Windows.