Invisibilia is the cool effect you achieve by replacing people in your photographs with their line drawings. It's not my idea. This guy has done many, and even written a nice tutorial for you -- which is great if you have photoshop. (tutorial link is at the bottom of his webpage) As you probably know, Photoshop is expensive if you don't have it, and very dense and hard to learn, if you do have it. It's probably a wonderful tool, but just reading through the tutorial was enough to make me shiver (and not in a nice way). So, here's a guide to making your very own Invisibilia to print, frame or whatever... using just the drawing tools you can find in an ordinary word processor, or in this case, PowerPoint 2007. (hey, you may know many of these tricks already. But I bet you learn at least one new thing. :-) Ready? Let's go.
http://www.instructables.com/id/Poor-Mans-Photoshop---Using-Powerpoint-to-make-In/