The latest release of the Linux kernel 3.3, is now available, this is the second release of the kernel in 2012 which brings with it the long-awaited merging of code from Google's Android project.

This is what particularly interesting to developers looking to boot Android or run apps on the stock Linux kernel and represents a resolution to the issues that kept the two apart for so long it's not the only new feature included. However optimized power management and other infrastructure that didn't make it this time will arrive in the next release that is 3.4

For a long time, code from the Android project has not been merged back to the Linux repositories due to disagreement between developers from both projects” the Linux 3.3 release notes state. 
“Fortunately, after several years the differences are being ironed out. Various Android subsystems and features have already been merged, and more will follow in the future. This will make things easier for everybody, including the Android mod community, or Linux distros that want to support Android programs.”
Also made into the release are improvements to file systems like Btrfs, memory management, networking, security and much, much more.