Sad to admit, but it has only been in recent years that I discovered that you need to oil cutting boards. Regular oiling will certainly extend the life of your wooden boards. I try to remember to oil mine once a month, or sooner if they look particularly thirsty! We have several Epicurean cutting boards which are awesome dishwasher safe boards constructed of a durable wood fiber composite material. We donated all of our plastic boards years ago when we discovered these! Since they occasionally go through the dishwasher after being used for cutting meats, those particular boards require slightly more frequent care to look their best.
I love finding extra uses for items we already have around the house, so I use my husband’s BBQ rib rack to hold all of my boards during the oiling process. I keep an oiling rag in a ziplock under the sink so I don’t have to get new rags messy every time. I will replace it after a several uses, but it does reduce the amount of oil needed, since it is already saturated.
I have used several products with clean ingredients. Most seem to contain food grade mineral oil and or beeswax.

• Start with a clean dry board.
• First I apply Block Bros. Block Oil (Rice Bran Oil and Lemon Oil). It smells really nice which is a bonus.
• I let the boards dry for several hours and then wipe off the excess oil.
• If I have time and energy I will layer on some Boos Block Board Cream (unbleached beeswax and food grade mineral oil).
• Again I let them sit for several hours and wipe off the excess before storing. This extra steps helps to seal in the oil, but I don’t do it every time.

Update:
One of you suggested trying olive oil and since I tolerate it so well in food, I gave it a try. It does work nicely, but just doesn’t last as long. Give it a go and see what you think.