I have put together a few free photography resources which I personally find useful, so I figured someone else may find them useful.

Aperture Chart

Useful chart showing the difference in camera apertures.

Download Aperture Chart

Moire Fringing Chart

Useful Moire Fringing chart to help you micro adjust lens focus.

Download Moire Fringing Chart

F-Stop to F-Number Chart

Chart showing relationship between camera F-Number and light F-Stop.

Download F Number to F Stop Chart