I've got two Shelties so lord knows, barking can be heard day and night here!

With Kaedyn (the worst barker), I squirt him with water everytime he barks. He loves to bark at the neighbors so everytime they're out there with their kids, I sit outside with Kaedyn on leash and try to get him used to the sounds. Everytime he barks, he gets a squirt but to get his mind off of it, I usually do some obedience work at the same time.

I'd probably try the citronella collar before the shock collar. But even before trying the collars, which seem to cost an arm and a leg, you could try something like squirting the dog with water or shaking a can of pennies.