Yesterday I watched someone wrestle to remove a background from a photo, using expensive software with a long learning curve, with lots of time consumed and much frustration. It took me exactly 4 seconds using...PowerPoint.
According to the Office Assistant: "You can create a transparent area in most pictures except in animated GIF. (Make these changes in an animated GIF editing program, and then insert the file again.)...The Set Transparent Color option is available for bitmap pictures that don't already have transparency information. It's also available for some, but not all, clip art." (Most of the art I use comes from clipart.com, and have had good luck with transparencies.)