Bitter Sweet II is a freeware dynamic processor for managing audio transients, available in RTAS VST & AU formats for Windows & Mac.
Description:
Bitter Sweet II is especially active on loud percussive tracks.
Turning the central button on the sweet side, decreases the transients amplitude. On the bitter side, the transients amplitude is magnified.
Bitter-Sweet also features a [...]

Audjoo has released a public beta of Helix, a freeware synth plug-in designed for huge and wide unison pads and leads.
Changes in this beta

The smallest sliders are scaled up slightly.
Filter Resonance is a modulation source.
Different filter types are grouped in tabs and colour coded.
EQ has properly labeled parameters.
Improved: Limiter filter type (attack depends on the [...]

Tagu Audio Line (TAL) have released Vintager, a free analog-style monophonic VST synthesizer. According to TAL, Vintager features “a good sounding non linear modelled 24dB lowpass filter, three bandlimited oscillators and accurate envelopes are the heart of this synth.”
Description:
This synth is suitable for all kind of typical analog sounds even percussion sounds. Also sounds that [...]

SonicBirth, a Mac OS X app for for constructing VST and AU plug-in instruments and sound processors, is now free and open source:
SonicBirth is now freeware, and open source (GPL). We are looking for developer to further work on and enhance SonicBirth. Work for the major version of SonicBirth is starting. This next version will [...]