Mozilla is at it again.In many ways they have revolutionized browsers with Firefox and all the plugins that make it a favorite amongst developers and "normal" users. They also had a fairly descent mail client in Thunderbird. Now, they are taking a stab at the future of email with Raindrop. From what I could see and read on the web regarding that project, it sounds very interesting.Mashable makes the connexion between Raindrop and Google Wave: both are trying to re-invent web based communication.
You might also be interested in ReadWriteWeb take on Raindrop or that of WebMonkey or GigaOM or TechCrunch