Cataclysm Zone Progression
The guys over at Project CWAL have done a fantastic job of producing these graphics, which illustrate well the levelling progression though zones now that The Shattering has taken place. If you are looking to level your new Night Elf Mage or Human Hunter, these should help you plan your route.
Please note that Outland and Northrend are completely unchanged by the Cataclysm, and as such remain level 59-70 and level 69-80 zones respectfully.
Eastern Kingdoms
Kalimador
Other Zones
Another fabulous graphic shown to me by Michael93 credits for this wonderful graphic go to Zeror and Rakkerzero! This image beautifully displays where to level and includes the progression through Outlands and Northrend into one clean picture.
Hope this helps you on your Journey through the new and shattered Azeroth!