The repeating quests that you are talking about are faction quests. They are repeatable because each time you complete them you raise your faction standing with whatever faction you were completing the quest for. Any NPC you see with a blue ? over there had has a repeatable quest available for you.
The following quests are repeatable (listed with the faction they raise):
For Alliance or Horde reputation
Cloth donation quests
For Darnassus reputation
“Morrowgrain to Darnassus”
“Morrowgrain to Feathermoon Stronghold”
"Staghelm's Mojo Jamboree"
For Stormwind reputation
“The Lost Supplies”
"One Man's Love"
For Ironforge reputation
"Wanted: MORE ORCS!"
"Arrows are for sissies"
For Gnomeregan reputation
"What the hoof?"
For Orgrimmar reputation
“Chen’s Empty Keg”
"Wanted: MORE DWARVES!"
For Thunderbluff reputation
“Morrowgrain to Thunder Bluff”
"Tuft it out"
For Darkspear Trolls reputation
"Darkspear Defense"
For Undercity reputation
"I've Got A Fever For More Bone Chips"
For Gadgetzan reputation
“Water Pouch Bounty”
For Argent Dawn reputation
Cauldron quests
Scourgestone Turn-in
”Healthy Dragon Scale”
For Timbermaw Furbolgs
“Feathers for Nafien”
“Beads for Salfa”
For Thorium Brotherhood reputation
Thorium Point quests
Molten Core item requisitions
For Wildhammer Clan reputation
“Troll Necklace Bounty”
For Wintersaber Trainers reputation
“Frostsaber Provisions”
“Winterfall Intrusion”
“Rampaging Giant”
For Steamwheedle Cartel
“Again With the Zapped Giants”
“Refuel for the Zapping”
You can look up most quests (what they are, what you have to do, who you get them from, etc.) around the web. I like
http://wow.allakhazam.com/, but take your own pick. Hope that helps you out.