Minecraft wiki entry for Bountiful_Update, associated text: Rebalances to the enchanting and repairing systems
Enchanting now consumes lapis lazuli
Beacons may be colored with stained glass
Mossy cobblestone, mossy stone bricks, and chiseled stone bricks now obtainable by crafting
Cracked stone bricks and sponge now obtainable by smelting
Item frames now emit a redstone signal, and can rotate to 8 directions
Daylight sensors may now be inverted
Powered activator rail now dismounts entities riding minecarts
Arrows decelerate much more quickly underwater, and extinguish if on fire
Improvements to mobs' behavior and AI
Most mobs can now swim - notably, Slimes
Most mobs can now pathfind as zombies have - notably, angry Zombie Pigmen
Skeletons flee from wolves
Spiders no longer see players through solid blocks
Iron Golems attack Creepers
Babies' growth can be accelerated by feeding them
Most mobs flee from a Creeper about to explode - though this feature was reverted in 1.8.1
Creepers, Skeletons, Wither Skeletons and Zombies drop their heads when killed by charged Creepers
Villagers
Now harvest crops
Breed only when willing
Have additional villager professions and trading schemes
Turn to witches when struck by lightning
Pets show death message if named with a name tag