I like this article because it's got a conceptual element: think of 4.0.1 as changes to your character, and think of Cataclysm in December (4.0.3) as changes to the world around you.
It also points to articles about each class and the changes to their talent trees. Paladins might find this discussion of Retribution paladins to be helpful:
This clarified for me the impact of picking a spec: it gives you most of the passive buffs that you formerly had to choose in the 41-point tree to make your spec work. So it definitely simplifies the process of setting up your talent build.
There's also a discussion of the rogue and its new Vanish ability here:
Warriors might want to read the warrior page:
Note that these were all written in September, based on play on the Public Test Realms, but they should still be generally applicable.
As time goes on, I am sure we will see much more information about the changes to the character mechanics. I'm eagerly awaiting the inevitable posting of suggested talent builds for the new 31 point trees. If anyone sees any of these come online, please let me know!