A site that only plays background noise from coffee shops and restaurants around the world to help you concentrate.
Simply Noise is an online white, pink, and brown noise generator. Good for sleep, deadening noise, concentration, and stress. There are also apps in the iProduct and Android stores that do the same thing (both $0.99us).
An online noise and sound generator. Has multiple categories and dozens of different sounds, from thunder to to rain to singing bowls, the wind blowing through a canyon, surf sounds, wind sounds in different locales, different voices, and different brainwaves. You can stack up to five of them in a sequence. You can download them, too! Updated periodically, so check back once in a while. The iOS and Android apps are out, too.