Developers and Android information fanatics, this is just a quick PSA that the official API overview, developer materials, and L Developer Preview reference are all now available on the Android developers site. The API overview can be found here, and the developer reference is right here.
If you want a detailed, piece-by-piece breakdown of the developer-facing changes in Android, the developer reference is by far your best bet. It includes tons of information, what's been added, what's been changed, and what's been removed in the "L" release. Detail API documentation is in there, too, meaning you can comb through for new features and functions (like we have most of the day).
You can also check out the entire L Developer Preview site, which includes primers on material design, notification design, designing for TV, and more. Check it all out at the links below.