Used book store, Book Off, 14 E 41st Street 
(between madison and 5th ave).. Shelves and 
shelves of used (but usually great condition) 
books usually between $1-3. :)  Much cheaper 
than Kinokuniya if you can find what you're 
looking for (I've gotten some Kenshins, X, 
Gravitations, and some yaoi books and 
anthologies from them before.. and they have 
quite a few other series that I recognized).  

I dont know of anyplace that sells cels though.

Goodluck :)