Anybody wanting to research this topic should also look at appropriate-economics.org. It is a veritable treasure trove of materials. In particular, the Complementary Currency Resource Center. A good Introduction,A Brief History of Interest and the articles by Michael Hudson are particularly good. There is also a Course on Complementary Currency Systems

Some readers may find Margrit Kennedy's website on Complementary currencies useful. Michael Hudson's website also has useful articles

That article on the history of interest is, well, interesting. I had no idea that it started as a means of sharing the results of natures reproductive ability.
That gives point to the Shakespearean horror at usury as a "breed of barren metal".
Thanks for the links Rajiv, they do look interesting and I will devote a few hours to exploring them properly when I can.

I would add this one:
http://www.financialsense.com/fsu/editorials/2006/0205.html
which explores some of the principles of money in a slightly humorous yet informative way.