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

2009
BIKE-O-RAMA: A Roundup of the Best in New Bikes, Bike Infrastructure, Blogs, Books and More
This roundup is a great resource of links to all things bike...

2008
Hot Japan's Cool Green Trends
Madeline Ashby reports on how Japan markets green tech and how other countries could follow their lead...

2005
Foresight in the Age of the Storm
Jamais Cascio reflects on Hurricane Katrina and says she was a reminder that climate foresight means more than imagining the worst and preparing for it...

Other recent "look backs":
August 25
August 26
August 27