We are training our puppy to go inside and outside. I use Arm & Hammer Puppy Pads inside and Wicket is very drawn to them. He will run to the pad (which we keep in a bathroom) anytime he has to pee, but he almost never poops on the pads. We still need to work on that. We supervise him constantly whenever he is out of his crate and are working on recognizing his signals (however subtle they are). I guess it's as much training for us as it is for them. I read an article about litter box training dogs this morning. The article suggested that you must first get your dog to eliminate in the same spot outside, then you can put the litter box in that spot outside (fill it with sod or paper) and see if he/she will eliminate in the litter box outdoors. If you have success with that, then slowly move the litter box indoors until you are confident that your puppy has the hang of it and then you can place it in its permanent indoor spot.
One of these days they'll get it...in the meantime, we all just have to be patient and celebrate like crazy when they get it right!