For the really awesome cels that Japanese 
collectors have, I recommend doing some snooping 
around the links pages of the Japanese cel 
dealers. You can also search for sites using a 
Japanese browser and kanji. It all depends what 
you are looking for? Anything series in 
particular? All of these ways should 
theoretically lead you to "public" galleries that 
might not make it onto English dominated links 
pages. 

But I agree peggichu, there are also so many 
really cool sites listed on the anime cels ring 
and even the Internet Guide to Anime cels.

Wendy