Freeware - Aelapse Tape Delay Spring Reverb VST Plugin

https://github.com/smiarx/aelapse

ÆLAPSE is a delay and reverb plugin. The delay is based on tape-delay mechanisms, while the reverb is inspired by (but not limited to) spring reverbs. It is designed for a variety of applications, from subtle spring-reverb guitar tones to dreamy synth pads, as well as dub-style snare sounds.

Freeware - REEV-R VST Plugin

https://github.com/tiagolr/reevr

REEV-R is a cross-platform convolution reverb with modulation for pre/send and post/volume signals.

Freeware - UnitedPlugins HyperspaceCore VST Plugin

https://unitedplugins.com/HyperspaceCore

Born from the acclaimed algorithms of JMG Sound's flagship Hyperspace, HyperspaceCore delivers a universe of spatial possibilities directly into your DAW. Go beyond simple room emulations and start designing truly unique soundscapes that breathe life and character into your music. For FREE!

Freeware - PSP Audioware PSP Chamber Reverb VST Plugin

 https://www.pspaudioware.com/products/psp-chamber

PSP Chamber is a freeware reverb plug-in that adds depth and dimension to your audio. Like classic hardware reverbs, it’s designed to emulate the acoustics of physical spaces of various sizes and shapes. The Chamber algorithm is carefully crafted to produce rapidly developing, dense reverberations with a smooth and natural decay. It’s a simple-to-use, great-sounding effect that’s a great go-to option for many tracking and mixing applications.

Freeware - Chaos Audio Freebie Plugin Bundle

https://chaosaudio.com/collections/tone-shop/products/freebie-plugin-bundle

Guitar stompbox FX

Get seven plugins, including reverb, drive, delay, and EQ, for FREE. 

Apollo - Classic Tube Drive 

Starlight - Shimmer Reverb

Cassini - Harmonic Reverb 

Transit - Digital Delay 

Booster - Clean Boost 

Spectrometer - 6-Band Guitar EQ 

Spectrobass - 7-Band Bass EQ

Freeware - Wave Alchemy Magic7 Reverb VST Plugin

https://www.wavealchemy.co.uk/product/magic7/

Experience the immersive sound of the legendary Bricasti M7 reverb for FREE with Magic7. Instantly bring three-dimensional depth to your music, effortlessly move between focused, tight drum spaces, airy vocal ambience, authentic rooms, expansive halls and warm chambers. Magic7 is available now as a FREE AU, VST3 and AAX plugin for macOS and Windows.

Freeware - Flo Audio Impulse Response Sets

https://floaudio.bandcamp.com/music

Assorted reverb IR sets

Freeware - Adam Szabo Solaris Reverb VST Plugin

https://www.adamszabo.com/vstplugins/solaris/

Winner of the KVR Developer Challenge 2023, Solaris VST reverb plugin is a mesmerizing tool that transports your audio into ethereal soundscapes. With its shimmering effect, it adds a celestial aura to your music, and creates cascading, sparkling reverberations. The Solaris plugin is your gateway to celestial realms, empowering you to create enchanting textures and transcendental atmospheres within your compositions. With its low CPU usage, it can also function as a modern reverb unit for many different applications. Solaris is available as a 32 and 64-bit VST2 and 64-bit VST3 plugin for Windows for free!

Freeware - Lotus Sound Audio Ocean Plate VST Plugin

https://www.patreon.com/posts/ocean-plate-100710016

Introducing OCEAN PLATE 🌊 – the epitome of warmth, depth, and sonic excellence in the realm of digital audio processing. Crafted meticulously from a stunning analog device renowned for its unparalleled sonic character, Ocean Plate reverb plugin takes your audio to breathtaking depths, enveloping it in lush, immersive ambiance reminiscent of vast, shimmering oceans ! 

With its rich, warm sound, Ocean Plate is not just a tool ; it's an experience. Whether you're producing music, mixing tracks or designing soundscapes, this plugin infuses your creations with an unmistakable analog charm that sets them apart. But Ocean Plate isn't just about reverb ; it's a complete sonic sculptor. Featuring a meticulously designed EQ section, you have total control over shaping your sound to perfection. 

Whether you're dialing in subtle enhancements or completely transforming the character of your audio, Ocean Plate empowers you to achieve your sonic vision effortlessly.

Freeware - Spectral Audio (legacy) VST Plugins

https://spectral-plugins.com/

3 free plugins: Lofi Cassette, multiband transient shaper, and multifx

Freeware - Gnarl Distortion VST Plugin

https://myroslavartiukh.gumroad.com/l/gnarl

Unique distortion plugin with a choice of distortion algorithms, filters for the dry and wet channels as well as a reverb effect.

Freeware - Variety of Sound epicCLOUDS Reverb VST Plugin

https://varietyofsound.wordpress.com/2024/01/15/epicclouds-released/

The ambient reverb is specifically designed to emulate the reverberation characteristics of large, open spaces or natural environments. It aims to create a sense of immersion and a feeling of being in a larger acoustic environment, such as a concert hall, cathedral, or outdoor setting. It typically has a longer decay time compared to other types of reverb and provides a very lush and expansive sound.

Freeware - Amalgamated Signals Nepenthe Reverb VST Plugin

https://amalgamatedsignals.com/nepenthe

Nepenthe is a reverb designed to be smooth, transparent, and easy to use. Nepenthe's algorithm is based on the concept of velvet noise. Rather than building echoes with a network of delay lines, it uses a predetermined set of randomly-generated echoes. This is a very simple design, which works well with modern CPU optimizations, so Nepenthe runs efficiently. Nepenthe is open source, and its code is annotated with detailed explanations of the design.

Freeware - Klanghelm TENS jr. Reverb VST Plugin

https://klanghelm.com/contents/products/TENSjr

TENS jr. is the little brother of the studio spring reverb TENS. It features TENS model 5 - tank A. The properties of the reverb have been extended compared to the unit from the late 70s/early 80s, it's been modeled after. So a single tank is stereo now and the range of decay times has been extended to 0.5 to 20 seconds. The reverb's character can be altered drastically with the associated horizontal fader. In contrast to classic spring reverbs found in guitar amps, organs or some synths, TENS jr. offers very high reverb density, fast build-up, and very low "boing" artifacts, making it sound almost plate-like. 

TENS jr. is freeware.

Make Your Own Reverb - Synthetic Impulse Response Tutorial in REAPER DAW

Freeware - IR Impulse Response Listing

https://www.kvraudio.com/forum/viewtopic.php?p=8553062#p8553062

Here’s a very long list of free reverb impulse response as well as other IR such as a guitar amp, speaker, amongst others.

Freeware - Platone Studio Flex Reverb VST Plugin

https://platonestudio.com/product/flex-reverb/

Flex Reverb by Platone Studio is a FREE, high-quality plate reverb with a handy graphic EQ. The plainly diffused sound of the automated reverb EQs can take your music (and your audience’s experience) to the next level. Listening to demos will prove, that this is the reverb you need. Easy to use, sounds convincing, and is completely FREE!

Freeware - ArtV Turbo Paco Reverb VST Plugin

https://www.kvraudio.com/product/turbo-paco-by-artv

Turbo Paco is an old-style Algorithmic Reverb, based on some own and other classic algorithms reverse engineered and posted by the user "Acreil" on this forum thread. This Effect is mostly about Allpass loop and Feedforward-Comb reverbs, with some few exceptions. There are some Choruses as a bonus.

Freeware - Recluse Audio Reflections VST Plugin

https://recluse-audio.com/ols/products

Simple, Easy, Sturdy, and low cost in processing power. Reflections is a powerhouse reverb/delay plugin that is designed to create swirling tails of hybrid digital signal processing. Consisting of a delay and a reverb module, Reflections allows the user to send audio between these modules. This creates a feedback loop between the delay and reverb which can enable 'no-input' mixing. Reflections was designed for vocal processing, and works exceptionally well when 'ducked' under the dry signal. 

Other free plugins available on the site.

Freeware - Raw Voltage Glory Synth and effects

https://rawoltage.com/downloadpage/

Several free synthesizers and effects plugins with free serial numbers for all.