http://www.ted.com/talks/william_li.html
I found this TED talk very interesting for a number of reasons. Firstly, it's a great guide to some of the foods we can include to help prevent new tumours and potentially fight the tumours we already have.
Secondly, it explains that everyone has cancer all of the time. It's the ability for those cancer cells to trick the body into treating them as 'normal' and provide them with a blood supply that causes the tumours to form.
This shifts my thinking around how to stay healthy, and how to encourage my family to stay healthy.
I'd also caution against some of the Dr Mercola stuff. Some of it is poorly supported by research and some of it is anti-chemotherapy.
I found this very useful when deciding to have chemotherapy:
http://www.sciencebasedmedicine.org/chemotherapy-doesnt-work/