Aside from any copyright issues that you may encounter, it's fairly easy to insert an image on the Web into a PowerPoint or Word file:
- Right-click (or control-click on the Mac) on the picture that you want.
- Select Save File As... from the popup menu. Save this file to a place you'll be able to find on your hard drive -- like your Downloads or My Documents folder.
Once the file is saved to your computer:
- Go into PowerPoint or Word.
- Select Insert, then Picture.
- Select From File. The picture will be inserted at its actual size right into your document.
Be sure to cite the appropriate source of the picture when you do this!