The "action" key is like any other keybinding. (By default its "F") You can change this in the options/controls menu.
The jetpack and helicopter hat now require either coal, charcoal, redstone, or blaze powder in your inventory to function.
You can now dye your armors just like leather armor. Be warned multiple dyes may produce strange results.
Glider - Makes you glide when action key is pressed
Parachute - Makes you fall slowly when action key is pressed
LifeVest - Makes you float in water, without holding space
Flippers - Makes you swim faster in water. Slower on land.
Heelys - Makes you move fast on land when action key is pressed (doesn't affect hunger)
JetPack - When holding jump, you fly up and are able to move through the air very fast
Helicopter Hat - When holding jump, you fly up slower then a jetpack and cant move very fast
Spring Boots - Make you jump 6 blocks high
Grappling Hook - When thrown (like a snowball) you will be teleported up to the block that the hook lands on
Scuba Helmet - Allows you to breathe underwater.
Mountain Boots - Allows you to climb any verticale surface including fences.
Ice Skates - Allows you to move faster when on ice. Slower on land.
Bananas - Similar to apples food-wise.