I've heard a lot of people using and recommending Mineral oil lately. But I have my doubts about that. Mineral oil is a by-product in the distillation of petroleum to produce gasoline and other petroleum based products from crude oil. Personally I would prefer to stick to all natural products on anything i prepare my food with.
We recommend using Grape seed oil to care for your wooden kitchen utensils and chopping boards. Any food grade oil is fine but some will tend to go slightly rancid, tainting the beautiful smell of the Camphor.
Grape seed oil is available from the oil section of most supermarkets and is about $12 for a 1L bottle, which if you are using it solely for chopping boards should last you a year or two!
Grape seed oil - Buy online