Particleboard cabinets: how best to protect them?

[Sandy Uhlmann]

My contractor installed particleboard kitchen cabinets that have a oak doors. These look great from the outside but the particleboard seems to scream "cheap". Although I can't do anything about how they look inside, I was wondering what the best way to protect them from water damage? Do I paint the insides? Place contact paper? Are their any other options?