Wikipedia
Ghash.io
GHash.IO is a bitcoin mining pool which allows bitcoins to be mined using personal hardware or cloud-based mining power. The collective value of the bitcoin mined in this pool was over $200 million in its first year. GHash.IO works in conjunction with the CEX.IO bitcoin exchange. Apart from mining bitcoin, GHash.IO hosts a Multipool for mining altcoins, as well as separate pools for mining Litecoin, Dogecoin, Auroracoin and Darkcoin. Altcoin mining options are available for independent miners, while bitcoin mining can also be done in the cloud by purchasing cloud-based mining power on CEX.IO Exchange.