Something that hasn't been talked about much is the fact that with Cataclysm many of the classic dungeons are being touched in some form or another. A few of them are actually having their intended level range altered rather dramatically. Below is the list of dungeons with each of their level ranges. You'll immediately notice that Dire Maul, Scholomance and Stratholme are now all lower level than they were originally.
These level ranges are from the dungeon finder. The first number is the minimum required to queue, the second is the highest allowed to queue.
# Deadmines (15 - 21)
# Ragefire Chasm (15 - 21)
# Wailing Caverns (15 - 25)
# Shadowfang Keep (16 - 26)
# Blackfathom Deeps (20 - 30)
# Stormwind Stockade (20 - 30)
# Gnomeregan (24 - 34)
# Scarlet Monastery - Graveyard (26 - 36)
# Scarlet Monastery - Library (29 - 39)
# Maraudon - Purple Crystals (30 - 40)
# Razorfen Kraul (30 - 40)
# Maraudon - Orange Crystals (32 - 42)
# Scarlet Monastery - Armory (32 - 42)
# Maraudon - Pristine Waters (34 - 44)
# Scarlet Monastery - Cathedral (35 - 45)
# Uldaman (35 - 45)
# Dire Maul - East (36 - 46)
# Scholomance (38 - 48)
# Dire Maul - West (39 - 49)
# Razorfen Downs (40 - 50)
# Dire Maul - North (42 - 52)
# Stratholme - Main Gate (42 - 52)
# Zul'Farrak (44 - 54)
# Stratholme - Service Entrance (46 - 56)
# Blackrock Depths - Prison (47 - 57)
# Sunken Temple (50 - 60)
# Blackrock Depths - Upper City (51 - 61)
# Lower Blackrock Spire (55 - 65)