You can't export slides within PowerPoint, but you can still work with individual slides outside it.
Recently, Stephen Lange, a longtime friend, asked know how to get individual PowerPoint slides into a video. For better or worse, we tend to think in "exporting" terms when a task like this comes up -- we want to export data from one application to another. Unfortunately, you can't do that in PowerPoint.
What you can do is save individual slides as separate files. When you want to use a slide in another medium, save the slide in a compatible format. For instance, to drop a slide into a video, first save the slide as an image file. Fortunately, that's simple:
From the File menu, choose Save As. In PowerPoint 2007, click the Office button and choose Save As.
In the Save As dialog box, locate a folder for saving the new image file.
Give the new image a name.
Now, here's the important part. From the Save As Type drop-down list, choose an image format -- .gif, .jpg, and so on -- one that's compatible with your video software.
PowerPoint will ask if you want to save just the selected slide or all of the slides in the presentation. Respond accordingly.
Once you have the slide(s) in an image file format, simply follow your video software's specifications for inserting the image file.
PowerPoint's part in the process is simple. It's knowing where to look that stumps most people.