And if I may, I would like to direct your attention specifically to the 10:00 PM GMT time slot (= 11:00 PM London, = 6:00 PM EDT), during which Jason Robertshaw of Cephalopodcast will be interviewing Kevin Zelnio of The Other 95% and Deep Sea News, Rick MacPherson of Malaria, Bedbugs, Sea Lice and Sunsets and me.
The theme is "The Other 71%" in reference to the amount Earth's surface covered with ocean. You can even join a chat room while the webcasts are live-streaming, a splendid chance to
More details on Cephalopodcast and Earthcast.
(Not wanting to be outdone by Cephalopod- and Earth-cast, it appears that NASA is also holding a special Earth Day webcast here. What a bunch of followers.)