I had an idea. Let’s share our favorite Free Plugins, Sample Libraries, Sound/Preset packs, so that we create a thread that becomes a resource bank (list) for composers. Please link to the product as well for convenience 
My Tips:
Spitfire - Labs Series
Project Sam - Free Orchestra Series
Orchestral Tools - Layers
Performance Samples - River Harp
Fluffy Audio - Haunted Choir
If you scroll to the bottom of the page, you can collapse the freebie section and there you find a collection of small freebies for various synths and one for Kontakt 6
My Favorite Guitar, Bass and Cloud Drum:
https://www.amplesound.net/en/download.asp
If you want to use sforzando or soundfonts i can also recommend:
to be continued…
KLANG their other CINEMATIQUE INSTRUMENTS instruments I find them extraordinary for the ambient / sci-fi genre.
CINEMATIQUE INSTRUMENTS
… and for the orchestral ensemble how not to propose SONUSCORE
SONUSCORE
Oh yeah … it takes a voice to season it all. Do you know Clare? It’s sweet and warm…by IVY AUDIO
CLARE SOLO
Thank you Elia, great suggestions. Klang seems especially interesting to me!
https://vstbuzz.com/freebies/pocketblakus-cello/?ref=3
pocketBlakus Cello
A very nice legato solo patch for kontakt.
I always share this in posts like these. LOL. Here you go:
https://www.sonible.com/balancer/
Balancer is available until May 4, 2020.
Some kind of eq/filtering to make instruments sound better.
I like this one. Not good for everything but on some instruments like guitar and piano I’ve got nice results. On choir it became a bit synthy but maybe it has to do with my samples.
I also add these very nice drum.
worth having a look at:
https://www.decentsamples.com/
i just tried the box violin and imho it sounds amazing.
(btw, with around 100MB its half as big as spitfire’s discover )
later on i will try the other instruments
David Hilowitz is a brilliant guy, his free libraries are interesting. I learned from him how to build DIY tools and how to create library on Kontakt.
https://valhalladsp.com/shop/reverb/valhalla-supermassive/
Reverb from Valhalla, seems very nice.
Oh yeah just saw this, a must have imo, Valhalla’s revers are legendary!
I find it rather disappointing to find that so many “free” orchestral libraries require the full version of Kontakt, which is not free.
I have been looking for any free sampler of a baroque recorder (for Mac–I have Logic Pro), or an Irish penny whistle. I have also been searching for a real bagpipe sound. Has anyone come across these anywhere?
I want to share some free EQ Plugins too
including SPAN which is very usefull.
http://www.ivyaudio.com/ i found this ones and the quality of the samples is remarkable, it has a piano, a solo voice, great drums kit and a tenor trombone
Never heard of them before, thank you for sharing Ismael.
Hey, here are the ones I gravitate to in most of my compositions
Pecheneg Tremolo This Trem is amazing, packed with a lot of great features I always use it!
As mentioned earlier, the projects sam stuff is great.
It isn’t free but it’s only like £4. A solo French horn by orchestral tools. Not sure if it’s still available but their layers orchestra is good too
Finally, a place to download a ton of home made sample libraries - piano book
Pianobook
These are good pipes Mikael!
I’ve never used bag pipes, I guess a Braveheart cover contest or something would require it 