Cels Forum

Be sure to buy an issue of Newtype-- it has a map for AWS.
Also, in Osaka, if you travel there, there's Artworks Osaka,
Panic Media Mix.  Animage has ads for those two stores in 
Osaka.  

Have fun-- get an English subway map for Tokyo, and then 
just match the kanjis up to the kanjis printed in small on 
the map, and you'll know where to go.  If lost, ask at a 
police koban, if you can find one.

For non cel stores, you'll find lots of posters in Nakano, 
and there's also a store with cheap used LDs, besides 
Mandarake.  Also try Akihabara, as they have a number of 
stores there.  I think this month's issue of Megami has maps
for stores in Akihabara.