Background noise - shhhhhhhh

I work in an open plan office and I often find it very hard to concentrate with so many distracting sounds, e.g. phones ringing, keyboards clicking, people talking so I've found some software that simulates more consistent background that helps block out other sounds - obviously I only listen to it through headphones but it really helps - and it's freeware - yay !.
You can get it from
http://www.serenesound.com/
Other uses are if you live in a noisy neighbourhood and have trouble sleeping because of that then this will help block out the noise by playing a noise that is easier to sleep to - apparently it's also good for getting babies to sleep and cheaper than an anechoic chamber.