Wikipedia:

A software synthesizer, also known as a softsynth or virtual instrument is a computer program for digital audio generation. It works like a common synthesizer, but is realized entirely in software. A software synthesizer will typically respond to MIDI calls like a normal synthesizer module. Propellerhead ReBirth popularized the software synthesizer. Software synthesizers can run as stand-alone applications or as plugins within other applications. Download freeware virtual instruments.

VST VIRTUAL INSTRUMENTS - FREEWARE

Cadencia

Foorius v.1.1

Mini Vurtbox v.1.0

Snorgan v.1.0

The Blue v.2.0

WNM-1 v.1.7 (Weird Noise Machine)

VstStudiMix v.0.7

Morphiza

Cellofan v.1.0

Saxi Player 1.0.3 beta

Ensembler

Micro-Organism VSTi

Intro

Polyvoks Station v.1.4

Lallapallooza   v.2.0.1

Amazing synthillator

Motion v.2.8

VB-1 virtual bass

Guitar Controlled Bass Synth v.3.0

Tromine Z v.1.1

<<  1, 2