try cel books. you can find artbooks at artstores 
for cheap sometimes that work well. basically they 
are like portfolios. archival paper with plastic 
sleeves. Noriko's anime store (online) has a good 
collection of them for sale as well as the cel 
bags to store them in.  many people say that 
storing cels carefully in a cel book is actually 
safer than framing them (framing can sometimes 
contribute to rot or fading or warping) while in 
your celbook the cel is exposed to minimal light 
and is held flat easily. 

make sure you separate your drawings from your 
cels (unless they are stuck) and dont store them 
touching each other...

there are lots of cel "storage" and care sites 
that I'm sure people could point you towards too 
:) I cant remember any right now off the t