I crack my neck, fingers and any other joints that will crack, all the time.
There is no conclusive evidence that doing so causes long-term damage (as it is simply releasing pockets of air/gas that build up in the synovial fluid, between the joints) though there is anecdotal evidence that doing so, over the long term may increase the chances of getting arthritis, but I haven't seen very much (credible) that actually supports this.