A list of free VST plugins, very subjective (stuff I use/d), certainly not complete; for more check out Plugin Boutique or KVR Audio or other such sites.

All Windows, most 64/32, some only 32. Mac version may be available some have other formats as well (DX, Mac AAX, RTAS).
If some links are dead, please let me know.

Free Reaktor Ensembles and Kontakt Instruments are not mentioned here as they require the full version of Reaktor/Kontakt and do not work with the players below.


INSTRUMENTS

Native Instruments
Komplete Players
Kontakt 5 Player, Guitar Rig 5 Player & Reaktor 5 Player with a quite substantial library
Mikro Prism for Reaktor Player (5 & 6)

Now available: Reaktor 6 Player, although it doesn’t appear to be part of the Komplete Players bundle.
Blocks Wired for Reaktor Player 6


Camel Audio
Alchemy Player
including 200 free sounds

Applied Acoustics Systems
Swatches
free sound compilation

U-He
Zebralette
Podolski
Tyrell N6
(download page in German, just scroll down until you see the word Download)

Ohmforce
Symptohm PE

UVI
UVI Workstation
comes with good library selection

CWITEC
TX16Wx
Sampler with sound shaping and modulation capabilities


EFFECTS

Toneboosters
4 Free Plugins
TB Isone Surround (Surround Simulation) especially useful - although headphone mixers should consider TB Isone (Speaker Simulation). Trial versions available - parameter saving disabled.
Old versions of the plugins available on the developer’s personal webpage as JB Plugins.

Flux::
some freeware:
BitterSweet v3
Sample Grabber
Stereo Tool

Plugin Alliance
4 freebies
bx_cleansweep v2 (Hi/Lo-pass filter)
bx_solo (M/S & Stereo widening tool)
Elysia Niveau Filter
SPL Free Ranger (EQ)

Ohmforce
Frohmage

Melda Production
MFreeEffectsBundle

Klanghelm
IVGI
distortion & saturation

Signaldust
64bit plugins and others
Abstract Chamber - reverb for large modulated spaces
Dust Equalizer - channel equalizer
Sweep - morphing filter
Tila2 room reverb - streamlined Tila

Cockos
ReaPlugs
The plugins that come with Reaper for those who do not want to / cannot use Reaper

Voxengo
Free VST plugins and AudioUnit plugins

Togu Audio Line
TAL-Dub and others

Cableguys
Pan-Cake
very useful panning tool

Steinberg
VST Classics Vol.1&2
Pick VST Classics and VST Classics Vol.2 resp. from the dropdown list


OTHER - Tools, Samples & Standalone Programs

Paul Nasca
PaulStretch
tool for extreme audio stretching

Computermusic
The Vault
Technically not entirely Freeware - requires the purchase of at least one mag. You’ll be able to download the special and sample pack(s) that come with that issue plus the core library

SPEAR - Sinusoidal Partial Editing Analysis and Resynthesis
Audio analysis tool, can also be used for sound design and creative editing

Sonic Visualiser
application for viewing and analysing the contents of music audio files. Basic functionality limited but many plugins available

IXI
IXI Audio
experimental project concerned with the creation of digital musical instruments and environments for generative music

Samplicity Bricasti M7 Impulse Response Library v1.1
Donationware, useful impulse responses

STN Impulse Sets

Acoustic Impulse Response Library

Praat: doing phonetics by computer

Leafcutterjohn
Forester
(tab Software - Subpage Forester)
Sound generation with samples

ocenaudio
ocenaudio editor
somehow reminds me of the good old CoolEdit, useful audio editor, multi-platform

Threechords
Hammerhead
Drum machine, has been around for a while (a long while); written by Bram Bos. Other nice programs available, too, most notably Moonfish, which I had lots of fun with. Sadly it doesn’t run on current Win versions (7, 8). Works on XP though, got it to run with a VM (might work with WINE in Linux)

Update 10 January 2016
Nice Round-ups here:
bpb Freeware Studio: Best Free VST Host Applications
Top 50 Freeware VST Plugins Of 2015!





TBC

Thanks for this. It prodded me to finally download and install the Komplete Players. Then to figure out how to record from the Player into my DAW (AcidPro6). Really nice sound from the Player and Reaktor and I guess now I have a platform for expansion via Native Instruments instruments.
Thanks for the effort that went into this post. I’m going to check out some of the other goodies too.

some nice plugins, all free, not sure of the maker

Cz10xv - Casio CZ1 emulator, few glitches but almost perfect sound, comes with huge library and if you register it you get a util to read sysex files from the original

Electrostudio Suite
Decent Juno 60, superb Mellotron and Minimoog (and a few more)- very flexible midi options so you can assign any parameter to any controller

SQL8 - Ensonique emulator- almost perfect emulation, amazing as the original was part analog- includeds all factory presets.

Prova Piano - no frills (not a single parameter) piano plug in. But it’s seriously the best sounding digital piano I’ve heard anywhere, great for stuff like ELP, Yes, Pink Floyd etc as it has a fat 70s sound to it.

Here is some of the free stuff for electronic creators I have been using for a while.

Windows(32bit) VSTi

VIRTUAL MODEL_MINI v.1.03 (zip 3,691MB)

VIRTUAL MODEL_PRO v.1.02 (zip 4,65MB)


ANALOG PACK 10 VST INSTRUMENTS v.2.54b (zip 3,69MB)

Davosynth v.2.54b (zip 1,68MB)

eSline String v.2.54b (zip 3,84MB)

Micromoon v.2.54b (zip 2,10MB)

Moon Sono Sx v.2.54b (zip 2,05MB)

Ocet Rhythm Machine v.2.54b (zip 2,19MB)

ODSay v.2.54b (zip 2,02MB)

OR2v v.2.54b (zip 2,92MB)

Rhythmus v.2.54b (zip 2,58MB)

Sxm June v.2.54b (zip 1,63MB)

Tapeotronic v.2.54b (zip 8,45MB)


All can be downloaded from this site

http://www.elektrostudio.ov...

Does anyone know a free soundfont editor? Vienna will only work with Creative AWE and Live! cards, I own one of these but it refuses to sit next to my EMU dsp cards as they share some hardware and the drivers can’t deal with it.

updated 3 Nov 2013

There’s a cool freebie called Maestro that is a typical monosynth bar the fact that the filters could be real Curtis chips, and it’s perhaps the first virtual analog which would fool me in a blindfold test. Very simple, no real-time controls bar mod etc as far as I can work out, but this has produced some of the fattest digital sounds going.