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

2009
Reader Report: The World's First Real Time Carbon Counter
Bryan Mitchiner reports on the launch of the "Know the Number" greenhouse gas emissions counter: the first real-time counter that advertises the increasing amount of carbon in the atmosphere...

2008
350 ppm, the Video
A catchy little video about the need to stabilize atmospheric CO2 at 350 ppm...

2005
Kenyatta Cheese: Citizen Television
Here're a number of community-based video sharing projects that are leveraging the distributed nature of the internet, giving anyone the ability to publish a "video channel" and making citizen broadcasting accessible to all...

Other recent "look backs":
June 23
June 24
June 25