An easy way to remove white backgrounds in seconds with Kill White
Kill White is a Photoshop Filter that actively removes white from an image (unlike the ‘Multiply’ blend mode), perfectly leaving the rest of the image, whether the image is black-and-white or color. However, this is not simple masking. Pixels that are partly transparent are altered so as to only remove the white portion. Shadows and gradients will remain in the image, only white is removed.
The example below should give you some idea of the effect:
Install instructions and download links for Kill White are on Mikeal's website. To install on a Mac, you'll need the free PixelBender plugin as well