iMorpheus has a great blog called the Gokurousama blog.
I say gokurousama when I get out of taxis, when someone as completed a chore or when I pass a gardner. It's similar to, but slightly different from another great Japanese word, otsukaresama. Otsukaresama is less about thanks but still acknowledging someone for some hard work. This is often said when toasting after a hard day of work or after working together on a hard project. Interestingly, working hard together is often considered more important than winning. This, in a way, is the backbone of the socialist work ethic that drives Japan. But I digress...
The Gokurousama blog and the pictures on it are a very good way to understand the Japanese way of gokurousama. It's also the spirit behind good service and a very nice way to show appreciation of good service. A simple gokurosama will go a long way and is much more respectful than flipping someone a hundred yen coin. iMorpheus has also started a Gokurousama flickr group and has linked the group to the blog so that others can post. You can learn more about it on his blog.
The next time you watch an old Samurai or Yakuza movie, listen for the boss say, "Gokurojyaaa" to one of the henchmen after he returns from killing a foe. ;-p