This is a way to access the graphics inside a PowerPoint presentation or Word document, without being resaved or resampled. I use this method when the author cannot locate the original files, but wishes to extract an image. This is for use with the XML based Office document formats (.pptx, .docx), and not the older style (.ppt, .doc) files.
Drag your .pptx or .docx files onto Stuffit Expander or Stuffit Deluxe, if you own it. Then navigate to the ppt folder, then media folder. Inside the media folder are all the images PowerPoint uses. If using Stuffit Deluxe, drag the media folder to where you want it extracted. If using Stuffit Expander, you already have the original files extracted.
Stuffit is used because it can expand the XML document package as a folder, while the Finder can't. The only drawback is filenames and file dates are not preserved. This is still better than trying to export an individual graphic that was previously imported to PowerPoint.
[crarko adds: I tested this with a PowerPoint file and Stuffit Expander, and it works as described.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100518154805806