Can dogs really learn to use a litter box? Sure! Dog box training probably isn't something you'd find dog owners regularly talking about, and although it may be unusual, it does have some advantages. Plus litter box training can be done at home, by any patient and positive dog owner.
One of the biggest advantages to litter box training your dog is the added freedom: your dog can go any time he needs to, even when you're not at home. It's convenient for the dog, and gives you more freedom to stay out longer (ever rushed home because you had to let the dog out?). Of course, since using the litter box doesn't come as naturally to a dog as it does to a cat, you will need to be prepared for several weeks of training plus an additional couple of months of monitoring / reinforcement.
There are lots of ways to train your dog to use the litter box. In general, though, here are a few things to think about:
You may need to modify the box to suit your needs. High sides will help to prevent streaks from male dogs lifting their legs. An open top will make it easier to clean.
Although the dogs that use litter boxes tend to be small breeds, large dogs can use them too! Try using a large plastic storage bin (modified to give your dog easy access to the inside).
Clean-up can be made easier by using litter box liners. Just tie up the liner with the used litter and discard.
Also make sure you have lots of cleaning supplies on hand. Get paper towels, odor and stain removers, bleach, etc. just in case your dog's aim is off. Laugh if you must, but accidents will happen!