Linux kernel 3.5 has been out for about a week already.
Most interesting in this release would be ext4 metadata checksums, and Android-style opportunistic suspend.
Checksums are used in modern filesystems to ensure integrity. With growing storage sizes the chances of failures on even good hardware increases dramatically, so being able to verify that files read back aren't corrupt is good. This feature only checksums filesystem metadata though which means actual user content isn't checksummed unlike more modern filesystems (Btrfs, ZFS). Read more.
Merging the Android codebase to Linux is as controversial as ever, but we're at least seeing some progress being made. Autosleep and wake locks add the mechanisms required to provide Android-style power management features into the kernel. Hopefully, this will help make Linux's power management even more awesome. Read more.
More details @ Kernel Newbies.