I just came across this excellent guide on how to take better photos. It is unusual in that it was developed with the research and development people in mind. It focuses on helping people take photographs that effectively convey messages, rather than on improving their ‘artistic merit’ per se.
Produced by Scriptoria Communications for the DFID-funded Research Into Use programme, the booklet provides excellent, simple advice on all aspects of digital photography for illustrating research results and communicating your findings. Well worth the read.