On the filesystem front, we had btrfs, ext3 and xfs getting active development (Why xfs? Beats me, but that's what the stats say), and a fair chunk of work on the whole fsnotify unification work. And the VFS layer got some TLC wrt ACL and private namespace handling.
On architectures: ARM, powerpc, mips, sh, x86 are the bulk of it. On ARM, the bulk is new platforms (u300, freescale stmp, whatever), there seems to be no end to crazy new arm platforms. On x86 (and at least some degree on powerpc), a noticeable part is the whole new perf-counter subsystem. Along with lots and lots of other stuff.