Hehe, the day after I saw this project we did them in college! And I got to show off my expert knowledge when the photographer said "These are photograms- Man Ray did them a lot"
"RAYOGRAPHS!" I said. Giggle!
This one was made by drawing onto tracing paper. It's a bit unclear because the tracing paper wasn't dead straight on the photographic paper- i like that though.
You can also do them by making stencils, that gives you a white background and black drawing.
In my humble opinion, the white on black is nicer though.