In PDF format:
Photo e-Tips: gathered from decades of professional experience this is a collection of illustrated photography tips to help you become a better photographer.
How to be a Great Photo Assistant: written as a guide for his own assistants, by professional photographer, Rob Walls. This e-book tells you how to make yourself indispensable if, or when, you are offered a job as a photographer's assistant.
Photographic glossary: an illustrated dictionary of literally hundreds of photographic terms with clear concise explanations and a hyperlinked index.