Black Hand can't sleep.
So you must all suffer my insomniacal meanderings and discoveries.
First one up: www.youtuberain.com
How this works is, any song that you think would go great with rain in the background and be played ad infinitum, you just add "rain" (minus the quotes) to the url while in youtube proper.
For example:
"https://www.youtube.com/watch?v=8yCyysCmhlQ" is the song "Ezio's Family" from the Assassin's Creed 2 soundtrack.
If you type in "rain" making it this:
"https://www.youtube
rain.com/watch?v=8yCyysCmhlQ"
then you now have that song with rain playing in the background on an infinite loop.
Personally, I've been listening to Cello Music by Adam Hurst.
http://www.youtuberain.com/watch?v=7RJRsEAKDNs?v=7RJRsEAKDNsBeautiful and sad in the same tone. Great music for writing I've found.