Harvard has published their Digital Photography course on Alison, a free certified learning website.
Here's the course description:
Digital photography technology is continually changing, however, the principles behind good photography don't. ALISON's free online photo course gives you the opportunity to gain extensive knowledge and understanding of digital photography including topics such as exposure settings, how to read and use the histogram, how light affects a photograph, how the camera sensor and lenses work, and how to process a photograph using computer software. You will also learn tips and techniques on what not to do when taking a photograph.Sign-up is easy and – as previously mentioned – free.ALISON's free online course is ideal for those who wish to increase their understanding of digital photography and want to know how to process and produce photographs digitally.