Pallet wood is a top choice for a lot of my projects because its free and you can often get amazingly beautiful wood, but I hate how long it takes to break apart the pallet and how my back kills me the next day, so I have found a solution.
Step 1: Sawzall the Nails
Take a sawzall with a compost blade (one that can cut wood and metal) and start cutting in between the slats and the base. Be careful to not let the blade swing towards you as the blade will encounter a lot of force and then suddenly nothing, so you do not want it to kick back at you.
Step 2: Usabule Wood
After that you will have a pile of full length pallet wood with no brakes or splits.
Step 3: The Pesky Nails
The only downside sometimes is there are still nails in the wood after, most of the lose nails will fall out due to the vibration of the sawzall and the ones that stay its really simple to get the nails out by taking an old screwdriver with a fine point and hitting it with a hammer. all the nails are supper lose with little holding them in so most will fall out with a few hits the ones that don't, well use the other end of the hammer