Linux kernel 2.6.25 has been released and available for download from the official website. After nearly three months of development and the merging of over 12,000 patches from almost 1200 developers, this kernel is now considered ready for wider use. Highlights of this release include the ath5k (Atheros wireless) driver, a bunch of realtime work including realtime group scheduling, preemptable RCU, LatencyTop support, a number of new ext4 filesystem features, support for the controller area network protocol, more network namespace work and much more. LWN has more information.
Related: How To Compile Linux kernel 2.6.xx.