Blizzard has put up an official preview of the new talent and mastery system that will appear in the next expansion, Cataclysm. MMO-Champion has also set up a talent calculator with all the new 31 point talents as well.
Blizzard put up an extensive preview of the new talent and mastery system. Blizzard stated that they felt the talent system hasn't aged well and this was their reason for the total revamp of the talent trees. The interface for talents will be receiving a change as well, and Blizzard put up a preview, check out the talent tree for warriors below (click for the full image).

Every class will have their three talent trees revamped, and each tree will have a final 31 point talent (as opposed to 51 point talents currently in game). Feel free to check out the talent calculator in the links below that MMO-Champion put together to play around with the new talents!
What do you think of the new changes? Do you like them? What do you think their effect will be on PvP and PvE play?

Links
World of WarCraft Community Site - Source
WoW Talent Calculator (MMO-Champion) - Play around with the new talent trees