Use the "Magic Wand" (no kidding, it's actually called that), and click on the white area. Click delete and now it should be checkered (meaning it's transparent).

Save the picture in .png, as it's a filetype that supports transparency.

Open the PNG in photoshop and use the paint bucket or color replace tool in the appropriate places to make white into transparency.

or use pixlr.com or the gimp

Use Photoshop Elements.

in gimp, Right-click the Layer on the right, and hit "Add to Alpha Channel" and use the eraser to get rid of the background

Use gimp. I always use it to customize the images, being of any format.