Google's just brought the official Android "L" preview site online, and while there's not much there yet, you know this is the place to check for info about the latest version of Android.
The site gives a quick overview of what's new in "L" (with a focus on what's relevant for developers), Android Wear, Android TV, and Android Auto. Hit up the link below to check it out - you can probably expect more information to be added here as I/O goes on.