Durotar is the starting area for both Orcs and Trolls, and the entry point for the front gate to Orgrimmar. There are three towns/outposts in the zone. Valley of Trials is the starter area, Sen'jin Village is at the far south, and Razor Hill, in the middle of the zone, is the major town.

Valley of Trials

Your Place in the World
Cutting Teeth
Sarkoth (troll laying on the ground at 40, 62)
Sarkoth (part 2)
Etched Tablet
Sting of the Scorpid
Vile Familiars
Galgar's Cactus Apple Surprise
Lazy Peons
Burning Blade Medallion
Thazz'ril's Pick
Report to Sen'jin Village

Ukor (52, 68)

A Peon's Burden

Lar Prowltusk (54, 75)

Thwarting Kolkar Aggression

Sen'jin Village

A Solvent Spirit
Practical Prey
Minshina's Skull
Zalzane
Report to Orgril

Razor Hill

Vanquish the Betrayers
Carry Your Weight (tower at 49, 40)
The Admiral's Orders (from chest at top of tower)
The Admiral's Orders (part 2)
Dark Storms
Encroachment
Break a Few Eggs
From the Wreckage

Misha Tor'kren (43, 30)

Lost But Not Forgotten

Rezlak (46, 22)

Winds in the Desert
Securing the Lines

Rhinag (41, 18)

Need for a Cure

Orgrimmar (Thrall)

Hidden Enemies
Finding the Antidote

Razor Hill

Margoz

Margoz (56, 20)

Skull Rock
Burning Shadows (drops from Gazz'uz)
Neeru Fireblad

Orgrimmar

Hidden Enemies (part 2)
Ak'Zeloth
Hidden Enemies (part 3)

Razor Hill

Conscript of the Horde