I've had good luck (defn: long term storage, no leaks) with water storage from Emergency Essentials. The 5 gallon container is especially good in this class, and only $9.95. Their 15 gallon drums are the bomb.

http://beprepared.com/category.asp_Q_c_E_160_A_c2c_E_ln_A_name_E_WaterStorageandAccessories.

Disclaimer: no interest in Emergency Essentials, just a happy customer.