The following method is applicable to 1.7 or above because this version only has one (/summon entity name coordinates) instruction, method:
/summon Pig ~ ~ ~ Enter the command to spawn a pig
/summon Cow ~ ~ ~ Enter the command to spawn a cow
/summon Zombie ~ ~ ~ Enter the command to spawn a cow Zombies
By analogy, the following are the English words for the creatures:
Cow - Cow
Chicken - Chicken
MushroomCow - Mushroom Cow
Bat - Bat
Pig - Pig
EntityHorse - Horse
Sheep - Sheep
Villager - Villager
VillagerGolem - Iron Golem
SnowMan - Snow Golem
Wolf - Wolf/Dog
Ozelot - Cat
Squid - squid
Zombie - zombie
Skeleton - skeleton
Creeper - creeper/self-explosion monster/JJ monster
PigZombie - zombie Pigman
Ghast - Ghost/Ghast
Enderman - Enderman/"Black Faggot"
Silverfish - Silverfish/Mite
Endermite - Ender Mite
Slime - Slime
LavaSlime - Hell Slime
Witch - Witch
Guardian - Underwater Guard
Blaze - Blaze
Spider - Spider
CaveSpider - Cave Spider
EnderDragon - Ender Dragon Boss
WitherBoss - Wither Boss
Giant - Giant Zombie
Non-creature:
Boat - Boat
MinecartRideable - Ordinary minecart
MinecartHopper - Hopper minecart
MinecartFurnace - Furnace minecart
MinecartCommandBlock - Command block minecart
MinecartChest - Box Minecart
MinecartSpawner - Monster Spawner Minecart
SmallFireball - Small Fireball (from Blaze)
Fireball - Fireball (from Ghast) )
Item - Item
LeashKnot - Rope Knot
Painting - Painting
LightningBolt - Thunder
ThrownExpBottle - XP bottle thrown
WitherSkull - Wither Skull (skull issued by Wither Boss)
EnderCrystal - End Crystal
FireworksRocketEntity - Issued Fireworks
Arrow
- Thrown arrow
ThrownPotion - Throwed potion
ThrownEnderpearl - Throwed ender pearl
EyeOfEnderSignal - Signal of the eye of ender
PrimedTnt - ignited TNT
FallingSand - falling sand attribute
ItemFrame - item display
XPOrb - experience orb
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unknown - fishing bait