16,000 BBC Sound Effects are made available by the BBC in WAV format to download for use under the terms of the RemArc Licence.
One of the best in their field, Project Sam offer free orchestral instruments (Registration needed)
The Spitfire Audio LABS programme is an infinite series of software instruments, free and easy to use; made by musicians in London for anyone, anywhere. They release one every month, as well as a bimonthly creative compendium, The Notebook. And in case you missed it, they are all FREE (Needs registration though)
Here are some demos:
Have a nice informative read about the Polish Radio Experimental Studio and download sounds from the 1960s-80s in Eastern Europe at Ableton.
Free Roland drum samples from Martin78.
Samples @ 48khz 16bit, some sounds were processed (exciter, equalizer)
recorded in 24bit by lexicon mpx-550, drum machine was powered by batteries
Free Mellotron sounds download from Bvker: 17 Serum presets, 17 Serum wavetables, 17 Serum noises (layered samples).
If you don´t know the Mellotron:
New Disco / House fusion sample pack from DDL. Features 10 Themes (Wav+MIDI), 120 BPM, All In Key Cm, 285 MB (Until April 5th 2019 exclusively at Beatport)