CEX.io is a new concept: Part exchange, part cloud mining service. We have been using it and we now recommend it to all our users. You essentially purchase the mining power from CEX.io in the form of GHS. Your GHS mines and can also be traded like a currency on their exchange. It’s really neat and ground-breaking stuff! The following is from their website. You can go there to read more or sign up.
CEX.IO is the first and leading commodity exchange in the Bitcoin community. Here you can buy or sell GHashes, Futures Contracts for the Bitfury ASIC chips or just trade on the increase or decrease of chip values.
We are the first exchange that offers you an opportunity to buy GHashes and avoid all the usual problems you can face when buying mining equipment, like the frequent delays in delivery, breakage losses, the need for a sufficient power supply or cooling devices, and many other things, that you will probably encounter.