Research has shown that creativity like writing is often difficult during complete silence. (I admit that as much as I'd like to, I can't write or even knuckle down to read a book in a too-quiet library).
Many writers have a relationship with coffee, and many enjoy the background noises in a coffee shop or cafe. Coffitivity.com, provides you with the noise of a cafe for background ambience. I'm listening, typing out this post, and holding a home-made Nescafé latte as you read this. Mmmm, it works.