Dustwallow Marsh storyline

Dustwallow Marsh is a level 35-40 zone in Central Kalimdor. Both the Alliance and the Horde have a presence here, at the human port city of Theramore Isle and the ogre-populated Brackenwall Village, respectively. In addition, goblins of the Steamwheedle Cartel have set up the town of Mudsprocket to the southwest.

Breadcrumbs

 * Hero's Call: Dustwallow Marsh!
 * Reinforcements From Theramore (from Southern Barrens)
 * The Call of Kalimdor (Alliance) & Flight to Theramore (from the Cape of Stranglethorn)

Theramore Isle
Calia Hastings:

Morgan Stern:
 * 1) Mudrock Soup and Bugs
 * 2) ... and Bugs

Lieutenant Aden:

Sergeant Amelyn:

After completing either Take Down Tethyr! or The End of the Deserters, Sergeant Amelyn offers:
 * The Hermit of Swamplight Manor (breadcrumb to Swamplight Manor)

At level 37, Guard Byron also offers:
 * Tabetha's Farm (quest) (breadcrumb to Tabetha's Farm)

At level 38, Lieutenant Aden also offers:
 * Mission to Mudsprocket (breadcrumb to Mudsprocket)

Shady Rest Inn quest chain
This chain starts with Guard Byron at Theramore Isle and spans much of the zone, going through two other quest hubs: North Point Tower and Tabetha's Farm.

Breadcrumbs

 * Warchief's Command: Dustwallow Marsh!
 * Next of Kin (from Southern Barrens)
 * The Call of Kalimdor (Horde) & Flight to Brackenwall (from the Cape of Stranglethorn)

Brackenwall Village
Krog:
 * A Shambling Threat
 * Darkmist Extermination
 * SMASH BROODQUEEN

Balandar Brightstar:
 * Twilight of the Dawn Runner

Nazeer Bloodpike:
 * 1) Theramore Spies
 * 2) The Theramore Docks

Draz'Zilb/Overlord Mok'Morokk:
 * 1) Identifying the Brood and Overlord Mok'Morokk's Concern
 * 2) The Brood of Onyxia
 * 3) The Brood of Onyxia (2)
 * 4) The Brood of Onyxia (3)
 * 5) Challenge Overlord Mok'Morokk

Tharg:
 * Army of the Black Dragon

Shady Rest Inn quest chain

 * 1) Inspecting the Ruins (Horde)
 * 2) Complete all of:
 * 3) *Suspicious Hoofprints (Horde)
 * 4) *The Black Shield quest chain
 * 5) *#The Black Shield (Horde)
 * 6) *#The Black Shield (Horde 2)
 * 7) *#The Black Shield (Horde 3)
 * 8) *#The Black Shield (Horde 4)
 * 9) *#The Black Shield (Horde 5)
 * 10) *#Return to Krog
 * 11) *Lieutenant Paval Reethe quest chain
 * 12) *#Lieutenant Paval Reethe (Horde)
 * 13) *#Talk to Ogron
 * 14) *#Questioning Reethe
 * 15) Complete both:
 * 16) * More than Coincidence
 * 17) * The Grimtotem Plot
 * 18) Seek Out Tabetha
 * 19) Raze Direhorn Post! (Horde)
 * 20) Justice Dispensed

Swamplight Manor
Mordant Grimsby:

Loose Dirt:
 * 1) The Orc Report / The Lost Report
 * 2) Captain Vimes (Alliance only)

Tabetha's Farm
Optional breadcrumb: Tabetha's Farm (quest)

Apprentice Garion:
 * The Grimtotem Weapon
 * The Reagent Thief

Apprentice Morlann:
 * Direhorn Raiders
 * The Zeppelin Crash (breadcrumb to Beezil's Wreck)

At level 38, Tabetha offers:
 * 1) Help for Mudsprocket (breadcrumb to Mudsprocket)

Beezil's Wreck
Moxie Steelgrille:

Mudsprocket
Breadcrumbs:
 * Help for Mudsprocket
 * Mission to Mudsprocket

Wanted Poster:
 * WANTED: Goreclaw the Ravenous

Gizzix Grimegurgle:
 * Catch a Dragon by the Tail

Brogg:

Nat Pagle
After reaching 200 skill in Classic Fishing, a quest unlocks that awards a useful fishing pole.
 * You Too Good. (optional breadcrumb)
 * Nat Pagle, Angler Extreme

Onwards to Thousand Needles
At level 38, breadcrumb quests to Thousand Needles become available in Mudsprocket:
 * To New Thalanaar from Thyssiana
 * To the Summit from Nyse

These have the advantage of providing you with a flight path to an otherwise out-of-the-way location on the other end of Thousand Needles.