Looking back one, two and five years ago today (give or take) on Worldchanging:

2009
World’s Largest Solar Power Plants With Thermal Storage To Be Built In Arizona
What's the easiest way to deal with the intermittency of many renewable sources of energy? Cheap storage. And what form of storage is much cheaper and has a much higher round-trip efficiency than electric storage? Thermal storage. Joe Romm presents concentrated solar-thermal power (CSP) as a core climate solution...

2008
Measuring Genuine Progress
Craig Neilson suggests moving from Gross Domestic Product (GDP) as the measurement system of choice for economic performance to the Genuine Progress Indicator (GPI), an alternative accounting system that internalises what are normally considered externalised costs......

2005
L'homme qui plantait des arbres
The English translation of Jean Giono's original essay, "The Man Who Planted Trees," is reproduced here in it's entirety...

Other recent "look backs":
April 19
April 22
April 23