Google has opened a public kernel repository, marked as experimental, for the Linux 3.8 kernel. The kernel repo is built from the standard Linux kernel, with Android modifications added by the folks in Mountain View working on the Android project.
The reason this is good news? 3.8 includes three important and interesting changes for mobile devices -- support for open source NVIDIA Tegra and Samsung Exynos DRM drivers, support for the Flash-Friendly File-System, and a lower memory footprint -- in some cases much lower. Having native support means less development time by Google or anyone else building the kernel for Android, and everyone loves more memory for apps instead of the system.
It's important to realize that this is by no means official support. Currently, Android 4.2.2 Jelly Bean ships with the 3.4 kernel on the Nexus 4, but versions 3.0 and 3.3 are supported as well for other Jelly Bean devices. Maybe we'll see 3.8 in the next version of Android.