since you are new, i think its ok to ask and i 
think the only problem with discussing Yahoo!
Japan here is that some people link to auctions 
others don't want people to see. *shrug* 
anyways... there is celga which i think 80% of 
people use (http://www.celga.com) There is Rinkya 
(http://www.rinkya.com/) which is a new service. 
and there is Mr. Sato (sorry i don't have his 
link handy, anyone know?) and for more info, just 
visited the board on aniemchaos (link in the 
previous msg) which has way more info

Hope ya find what you're looking for ^__^