Mojang: We now have a Minecraft Developers blog!
Mojang have started up a blog specially for them to communicate progress on things like the Minecraft API. It aims to help share more technical details with the community and developers and organise discussions. It appears that EvilSeph (Warren Loo), one of the Bukkit guys who Mojang employed, is the driving force behind this.
The blog is called Minecraft: Into the Void