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

2009
Eyes On The Street: Try A Bixi Bike On For Size At Union Square
A reader sends in a photo of a temporary installation of a Bixi bike-share station on the west side of Union Square, and Ben Fried suggests that this is a glimpse in to the future...

2008
Headlines from Worldchanging Seattle (8/22/08)
The Worldchanging team had walkability on the brain and shared six stories from Worldchanging Seattle about sidewalks, LID, architecture and community in Seattle...

2005
Retro: Leapfrog 101
Alex Steffen recommends Jamais Cascio's post Leapfrog 101 as the best short-course explanation of the idea and its implications he's ever seen...

Other recent "look backs":
August 18
August 19
August 20