Clipping Magic is a new web tool to easily remove the background from images. You upload your image, mark the image with the website’s red and green tools (red for background, and green for foreground), and voila! The areas marked red will be removed from the image and you can then download the edited image file. This is a great alternative to using Photoshop to remove a background, especially for removing image backgrounds on the fly.
Clipping Magic is currently free while the service is in alpha.