"This document explains some of the new functionality to be found in the 2.5
Linux kernel, some pitfalls you may encounter, and also points out some new
features which could really use testing."
There's a lot of good stuff here, and worth checking out for a glance at what'll be coming in 2.6.
Full document:
http://www.codemonkey.org.uk/post-halloween-2.5.txt