Remove the background from an image in PowerPoint 2010
PowerPoint 2010 offers a cool new 'Background removal tool' which will make image editing quite a fun. As per Microsoft "Unlike similar tools, the Office Background Removal tool doesn’t just select color ranges or trim to a border you draw. Background Removal uses new capabilities and algorithms from the Microsoft Research in Cambridge, UK to achieve better results automatically with very little effort or fine tuning from the user."
The new Remove Background tool as claimed by Microsoft is intelligent enough to identify background and forground thus making the task of background removal easy. You just need to select the area(marquee selection area ) of the picture which you want to keep or use on the slide. For refinemnet you can mark the areas you want to keep or remove manually.
You can find more information about image editing in PowerPoint 2010 on Microsoft blog.