The newest kernel 3.6 has been released yesterday. Comparing to kernel 3.5, there are many changes and fixes in 3.6, according to Linus Torvalds.
However, here are the 4 important new features in kernel 3.6:
1 - Hybrid sleep
This is a combination of sleep mode and hibernation. It will copy the contents of RAM to the hard drive, as in hibernation, and then entering sleep mode. The benefit of this new feature is that after sleeping, the computer can not only resume immediately, but it also won't lose any data if power is lost. If power is interrupted, the device will resume from the hibernated image; if not, it will resume normally and the hibernation image will be discarded.
2 - Better drivers
Just like every other update, kernel 3.6 offers better hardware support than the former versions. Of particular note among those included in this release are drivers targeting Sony and Apple vendor-specific devices.
3 - TCP fast open
In kernel 3.6, this Google-developed feature will be supported on the client side (support for server will probably come in the next kernel). According to the release note, this new feature can improve the page load speed up to 40% on popular websites.
4 - Improved memory management
Among several changes designed to improve memory management, finally, is a new feature that allows swap read-ahead IOPS (input/output operations per second) to be merged, thereby improving throughput while also lowering CPU consumption.
Read more about the new features of kernel 3.6 here