Pinhole Photography is basically photography without the use of a lens, it is a great way to experiment with photography. You can create pinhole photo's by making cameras out of tins and exposing directly onto photographic paper or if you lack the access to darkroom facilities you can use your SLR with the lens detached. For detailed information on how to create your own pinhole photographs follow the link below.
Below are some pinhole photographs that I really like.
Justin Quinnell - Pinhole photography taken from inside the mouth