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

2009
Travel Matters: Paid Vacation Law & Sustainable Tourism
Carissa Bluestone explores the place at which vacation law closely intersects with the future of sustainable tourism...

2008
Toilet to Tap or Perfectly Potable? California Uses New Treatment Technology to Increase Water Resources
As the population swells, the aquifers dry up and the surrounding area snow packs melt, southern California is looking for ways to secure their water supply. Sarah Kuck reports on California's Orange County Water Replenishment System...

2005
Design, Innovation and World-Changing
Jamais Cascio shares Luke Wroblewski's brief-but-important comparison of different concepts of strategy and innovation, based in part on recent analyses of the role of creativity and design by Tim Brown, Roger Martin and Richard Florida...

Other recent "look backs":
August 11
August 12
August 13