ChatterBlocker

Chatterblocker isn't a web-based application as SimplyNoise.com is, this is a piece of software you'll have to spend $19.95 on if you find it works for you. But the idea is the same, to mask background chatter in offices and other noisy environments by introducing audible interference. Rather than simply use white or pink noise, the application uses a mixture of musical, human and natural sounds and the user can vary the effects to find the best choice for a given situation. I did find that the application offered me some relief in a noisy family living room, and if I had to work in this sort of environment regularly I'd definitely give this a go. There's a free trial, so it's worth a download if coping with environmental noise is an issue for you.