We have used the Johnson and Johnson Vapor Bath, which works really well to loosen the congestion right before bed. Then we put a pillow UNDERNEATH THE CRIB MATTRESS where our kids lay their head to elevate it somewhat so they can breathe easier.
Our kids recently had colds at the same time and they share a room, so we used .....I think it was called the Sudacare Fan - works on batteries and is a fan that blows the homeopathic medicine throughout the room - smells like cherry Vicks - works great and the fan can be placed as close or far away from the kids as you want.
Good luck - I hope your son feels better soon!