Rabbits are social creatures and they thrive well when they are housed with others of their own kind. If you have one rabbit right now, you should consider bringing home another one so they can keep each other company.
Rabbits that are housed together have also been shown to be less likely to engage in undesirable habits such as destroying things. A bored rabbit is a perfect ground for the development of undesirable behavior.
Rabbits of the same sex can be placed in the same enclosure. But rabbits are very prolific! And if you are not ready to care for a litter of little bunnies, it is a good idea to have them spayed (females) or neutered (males). Take note that 3-4 weeks should pass after surgery before they can be placed together in the same cage in order to prevent mating and pregnancy. You can click on the link to know more details.