Synthesizers

Applied Acoustics Systems
Develops Tassman and Lounge Lizard, virtual instruments based on physical modeling.
http://www.applied-acoustics.com/

Arturia
Offers Moog Modular and CS-80V, a reproduction of the Yamaha CS-80. Specifications, audio samples, support, and download area.
http://www.arturia.com/

AudioRealism
It develops Bass Line, a bass emulator. Main features, audio samples, support area, purchasing information.
http://www.audiorealism.se/

Beatcraft
Virtual drum machine software. Make your own beat with 266 different drum sounds.
http://www.acoustica.com/beatcraft/

Big Tick Audio Software
Makers of the CheezeMachine, TickyClav, Angelina and Rhino software synthesizers.
http://bigtick.pastnotecut.org/

Brainspawn
Offers the Forte soft-synth controller. Also a tone generator and a spectrum analyser.
http://www.brainspawn.com

Camel Audio
Featuring Cameleon 5000 and some effect plug-ins. Description, screenshots, reviews, company information.
http://www.camelaudio.com/

CreamWare
Makers of DSP and synthesizer software and hardware for PC and Mac.
http://www.creamware.com/

Crystal
Semi-modular synthesizer featuring both subtractive and FM synthesis. Description, user guide, screenshots, downloadable demo.
http://www.greenoak.com/crystal/

Cutter Music
Creators of SawCutter softsynth.
http://www.cuttermusic.com

Devine Machine Software
A loop workstation VSTi, also offers the free LiveSyncRecorder PC VST plugin.
http://www.devine-machine.com

Disco DSP
Company that develops Discovery and Vertigo and some effects. Description, screenshots, audio samples, downloadable demos.
http://www.discodsp.com/

Doggiebox
Percussion sequencing application (drum machine) software for Mac OS X. Overview, screenshots, FAQ, mailing list and support area.
http://www.doggiebox.com/

FabFilter Software Instruments
Develops FabFilter One, a monophonic lead synthesizer in VST and AudioUnit format. Audio samples, downloadable demo.
http://www.fabfilter.com/

Garritan Orchestral Libraries
Developing intruments based on Kontakt software technology. Audio samples, features description, news and purchasing information.
http://www.garritan.com/

Grapesynth
A software synthesizer loosely based on the CZ series synth engine.
http://goombas.org/fullview.asp?id=57

iDrum
Drum machine for Mac OS X: overview, screenshots, main features, purchasing information.
http://www.bitshiftaudio.com/products/audio/idrum/

Kiesel Software
Developers of the Helga softsynth.
http://www.kiesel.is/

KVR Audio
Software synthesizer news, resources, information and reviews.
http://www.kvraudio.com/

Lapjockey
Reason ReFill suppliers.
http://www.lapjockey.com

LinPlug Virtual Instruments
[Win - Mac] Several VST synths: screenshots, audio samples, download and support area.
http://www.linplug.com/

MachFive
Overview, screenshots and technical specifications of this sampler from MOTU.
http://www.motu.com/products/software/machfive/

Manyetas: Ritmo
Audio Unit drumsampler for Mac OS X. Feature description, screenshots, audio samples, forum, downloadable demo and online ordering.
http://www.manyetas.com/ritmo.html

MHC Synthesizers and Effects
Space Synthesizer, Fatsondo Synthesizer, Voxynth, FlexFX, Space Effect, VST Plugins for Windows.
http://www.mhc.se/software/plugins

Morphology
Feature description, screenshots and system requirements of this instrument by Zero-G.
http://www.zero-g.co.uk/index.cfm?articleid=787

Muon Software Ltd
Develops virtual instrument plug-ins for use with music recording software.
http://www.muon-software.com/

Musicrow
Features several Instruments and Reaktor-5 ensembles.
http://www.mcrow.net/

MX4
Virtual instrument from MOTU: overview, technical specifications, audio examples.
http://www.motu.com/products/software/mx4

Nyr Sound
Developer and supplier of synthesizers including Chaosynth, Ice and Fluid.
http://www.nyrsound.com

The Oddity
Virtual instrument modeled on the classic ARP Odyssey. Features, audio samples, system requirements, screenshots.
http://www.gmediamusic.com/gforce/oddity/oddity.html

Pluginspot
Distributors of the affordable DX-10, WASP and MDA piano softsynths.
http://www.pluginspot.com/English/frames.html

Prophet 64
Use your Commodore 64 as a TB-303 sequencer with a Prophet 5-like interface. Includes a random composer pattern generator.
http://www.prophet64.com

Psychic Modulation
[Win] Features several VST instruments by Jack Resweber. Downloadable demos.
http://www.psychicmodulation.com/

rgcAudio Software
Creators of the Pentagon and (free) Triangle softsynths.
http://www.rgcaudio.com

SampleTank
Sound module which combines into a VST instrument, a sampler/synth engine with multisampled sounds.
http://www.sampletank.com/

Sfx Audio Compiler System
Integrated development system to generate real-time audio effects and synthesizer instruments using SAOL with SoundFont 2 for Structured Audio Score Language (SASL) and MIDI compositions.
http://www.angelfire.com/electronic/sfx/

SoftPlug
Adventus VST synth offers leads, pads, strings, basses, organs and pianos, for live performance work or sequencing. Demo available.
http://www.softplug.com

SoHa Sound Design
Makers of Sonata, a VST soft-synth for leads and pads
http://www.sohasound.com

Sonic Charge µTonic
[Win] Drum and percussion synth combined with a pattern based engine. Features, audio samples, downloadable demo, purchasing information.
http://www.soniccharge.com/

Sonorous codes
Creators of Atmogen, the visual additive software synthesizer.
http://www.sonorouscodes.net/

Spectrasonics
Virtual instruments like Stylus, Atmosphere and Trilogy. Audio samples, worldwide distributors, online ordering.
http://www.spectrasonics.net/instruments/index.html

Stomper
Non-real time 808 and 909 drum synthesiser.
http://www.lysator.liu.se/~zap/stomper/

Synapse Audio Software
Makers of Orion, Hydra and Scorpion. Screenshots, support and download area.
http://www.synapse-audio.com/

SynC Modular
A software synthesizer for Windows 95, 98 and NT4.0. Allows up to 16 voices. Available for free download.
http://www.mtu-net.ru/syncmodular

Syntheway
Instruments and effects such as DAL Flute, Master Hammond B3, Realistic Virtual Piano, Fantasize SoundFont Player
http://www.syntheway.net

Synthogy
Company that develops Ivory, a sample based piano virtual instrument. Features, screenshots, demos, purchasing information.
http://www.synthogy.com/

Toontrack
Develops DFH Superior, a drum and percussion virtual instrument. Main features, forum and support area, audio and video demos, purchasing information.
http://www.toontrack.com/index_samples.shtml

Tweakbench
Creators of freeware VST Instruments for Windows.
http://www.tweakbench.com/

Twitch
[Win] Drummachine allowing sample destruction, degrading, layering and reshaping. Screenshots, manual, download area.
http://www.majken.se/twitch/

VirSyn Software Synthesizer
Develops Tera and Cube. Description, downloadable demos, support area, company information.
http://www.virsyn.com/

Virtual Instruments
Magazine about the world of softsynths and samplers. Online subscription for both the paper and digital edition.
http://www.virtualinstrumentsmag.com/

Virtual Synth Page
A resource about software synthesizers including background information and detailed reviews.
http://www.markwhite.com/vsp/

Visiomedia
Software synthesizers, music production systems, audio and video processing software.
http://www.visiomedia.com

VocalWriter
Synth that sings English lyrics for Mac OS X: specifications, audio demos, download and purchasing information.
http://www.kaelabs.com/

Way Out Ware
TimewARP 2600 Arp 2600 emulator. RTAS plug-in.
http://www.wayoutware.com

Yellow Tools
Development of sound libraries and virtual instruments such as Culture, Majestic and Candy. Feature description, support area and purchase information.
http://www.yellowtools.de/

Yohng.com
Develops some virtual instruments and effects. Feature description, audio samples and demos available, screenshots, purchase information.
http://www.yohng.com/

Zebra
Description, technical overview, screenshots, download area and purchasing information about this synth that combines subtractive and additive synthesis.
http://www.u-he.com/zebra/