- Insert photos onto a blank slide.
- Resize, crop, and add shadows using the Drawing tools.
- Export by selecting File: Save As, and change the format from PowerPoint to JPEG.
[robg adds: Yes, this can be done relatively easily in any major graphics program. But sometimes, it's just easier to use a simpler solution. I actually use Keynote for this quite often, as I like it's layout and graphics options. It doesn't, however, have a Save as JPEG option, and using a PDF export, you'll lose transparency. So I just take a screenshot of the final layout and then use that...]

