Below you’ll find a list of attunements / keys that you’ll need for Burning Crusade.
The Shaterred Halls Attunement Guide
Shadow Labyrinth Attunement Guide
Arcatraz Attunement Guide
Karazhan Attunement Guide
Tempest Keep, The Eye Attunement Guide
You can also visit each individual zone to find out their heroic mode requirements by going to the zone page at:
http://www.ampwow.com/wow/viewZones