I listen to this whilst surfing the web:

https://www.youtube.com/watch?v=HZLlumRLsbQ

Also handy:

https://coffitivity.com/

http://www.getworkdonemusic.com/

This is a personal favorite too - Star Trek TNG Ambient Engine Noise (Idling for 24 hrs):

https://www.youtube.com/watch?v=ZPoqNeR3_UA

Personally, whilst coding, I enjoy absolute terrifying silence.