RunBeerRun has released Alt Resonance, a free amplifier simulator for any instrument (guitar, bass, synth) in VST format for Windows.
It uses simple filtered feedback as a resonance source. It has a 3-band crossover with per-band inverting, a bass booster, and optional clipper/limiter output protection.
It was built for hardware guitar effects pedals and amp sims that lose presence when plugged into a computer.
More info: Alt Resonance free amplifier simulator