When you need the object of a picture, but not the background, it can be a pain to separate them, especially if you don't have Photoshop. As long as you don't need pixel-perfect control, Background Burner can do the grunt work for you in a jiffy.
The web app starts by analysing the photo and presenting you with a few options for what it thinks is the right parts of the picture to remove. You can then touch it up with a couple of brushes to either include or exclude certain parts. The edges aren't always perfect, but it gets the job done.