1. Descrease weight of your photos deleting it's meta. Use "jhead" for that. Or just move all graphics to another hosting provider with lower prices for BW and make them to load through ip or sub-domain.
2. Use compressing for html files. For apache here is the mod :
http://www.innerjoin.org/apache-compression/howto.html
I don't really know any other methods of decreasing BW.