This is also a good indicator of where to level...
http://www.worldofwarcraft.com/info/bas ... eons.shtml
World Dungeons
Deadmines - Level 15-20 - Westfall
Wailing Caverns - Level 15-21 - The Barrens
Gnomeregan - Level 24-33 - Dun Morogh
Razorfen Kraul - Level 25-31 - The Barrens
Blackfathom Deeps - Level 20-27 - Darkshore
Shadowfang Keep - Level 18-25 - Silverpine Forest
The Scarlet Monastery - Level 30-40 - Tirisfal Glades
Uldaman - Level 35-45 - The Badlands
Razorfen Downs - Level 35-40 - The Barrens
The Sunken Temple - Level 44-50 - Swamp of Sorrows
Blackrock Depths - 48-56
Blackrock Spire - 53-60
Strathome - 55-60 - Eastern Plaguelands
Other Minor Instanced Areas
The Stockades - Level 23-26 - Stormwind
Zul'Farrak - Level 43-47 - Tanaris Desert