Matt Montagne has spearheaded this effort, with a great deal of support from Doug Symington, Jose Rodriguez, and others in the EdTech community. Jason Robershaw created an outstanding promo explaining what EarthCast is all about, and how you can participate.
Students and teachers are participating from the United States, Mexico, the UK, and Germany. You can listen live, participate in the text chat, or use Skype to call in and share your views.
While the project ends at 9PM EDT, much of the archived audio will be available afterwards on the web site.