Evolution Of Sound
Tutorials & Free Samples. Free Soundsets for Sylenth1/Serum/Spire etc.
VST Instruments for 10$ or more if you want – for charity.
Mixing Infos and Free EQ Cheat Sheet.
Besides their service, they have a good Blog with good articles worth reading.
BBC Sound Effects
“These 16,000 BBC Sound Effects are made available by the BBC in WAV format to download.”
Sell Your Beats Here for free and more stuff.
Dance MIDI Samples
You can buy samples here and they have good articles which help you produce music.
KB6 Drum Samples Archive
FREE drum samples to download.