Linux Kernel version 3.1 has popped its head up and offers support for a range of technologies such as Intel's Ivy Bridge and Cedar Trail chips, NFC and drivers for Wiimotes. It also has improved power management. It's available to download right now, but of course you may want to wait for the distro of your choice for an official update or release.
Its own summary sums it up quite well:
Support for the OpenRISC opensource CPU, performance improvements to the writeback throttling, some speedups in the slab allocator, a new iSCSI implementation, support for Near-Field Communication chips used to enable mobile payments, bad block management in the generic software RAID layer, a new "cpupowerutils" userspace utility for power management, filesystem barriers enabled by default in Ext3, Wii Controller support and new drivers and many small improvements.
A few features that I will point out is the new architecture: OpenRISC. OpenRISC is an Open Source CPU from the OpenCores project that brings to the world of hardware all the same advantages that Open Source software has done so for a very long time now. Dynamic writeback throttling is also included, with "Writeback" being the process of writing data from the RAM to the disk, and in this context throttling means blocking processes temporarily to avoid them creating new data that needs to be written, until the current data has been written to the disk.
This has been impoved also, with the new code avoiding these situations of suboptimal performance and bottlenecks. There are so many new features, I urge those who are interested to check out the feature list here.