To be planted with carrot seeds on farmland, makes for an excellent stack food as it grows quickly (3 visible stages) and replenishes 2.5 hunger points at 0.2 nourishment.
It can be used as an ingredient in Sammiches and Salads. Who can possibly resist the crazy carrot-tofu-mayo supercombo sandwich?
Since the 1.4.2 Minecraft patch, carrot are disabled.