I guess it depends a lot on your level and where you prefer to keep your hearth. Ruling out the alliance cities, I guess Ashenvale might be convenient for a mid-level character.
Kalimdor
Teldrassil: Dolanaar
Darnassus: Temple of the Moon
Darkshore: Auberdine
Ashenvale: Raynewood Retreat, Shaeldryn's moonwell, east of Iris Lake, Southern moonwell, east of Mystral Lake
Stonetalon Mountains: Stonetalon Peak
Moonglade: Nighthaven
Thousand Needles: Thalanaar
Desolace: Nijel's Point
Feralas: Feathermoon Stronghold, Dire Maul
Felwood: Jaedenar, Ruins of Constellas (corrupted but usable)
Silithus: Cenarion Hold
Tanaris: Caverns of Time
Eastern Kingdoms
Stormwind
Duskwood
Outland
Zangarmarsh
Blade's Edge Mountains
Terokkar Forest