A bit late posting this (been a bit of an absentee amateur astronomer lately thanks to a busy schedule at work), but thought I would share what it looked like to see the lights of downtown Dallas go out in celebration of Earth Hour, an event organized by the World Wildlife Fund to bring attention to the need for solutions for global climate change.
On March 28th, 2009, the Texas Astronomical Society of Dallas hosted an Earth Hour star party on the roof of West Village in uptown Dallas. TAS members brought out with their telescopes and the Dallas Museum of Nature and Science Planetarium staff presented shows in their portable planetarium. The real excitement started at 8:30 pm as downtown lights went out. What a spectacular site!
Also, check out this article for great shots of other major cities around the world celebrating Earth Hour.