The 'No Poo' movement, as it is called, has been growing in popularity over the last few years, as being a dirty hippy who doesn't wash their hair comes back into fashion.
Well, not quite - people are still washing their hair. Just not with the chemicals in shop-bought shampoo.
While initially quitting shampoo in favour of soap, baking powder, vinegar or any other number of things No Poo enthusiasts swear by will make your hair temporarily gross as your scalp learns to stop producing so much oil, they all report that their hair is healthy and looks better than ever after a few months.
Over at The Hairpin there's a good guide on how to quit shampoo if you're so inclined.