[jbmny]

MyNoise is a really high quality, well maintained website run by a single person. He even goes out and does his own field recordings. I highly recommend it.

[akx]

... With microphones he builds himself, too. https://mynoise.net/microphones.php

[car]

And really cheap, just $650!

[b3morales]

+1 There are associated mobile apps as well, that are not the prettiest, but provide access to the whole library. Really a gem.