Give Eobot.com Cloud Mining a try! Can get started with $10 using PayPal and Eobot is the easiest, cheapest, and best way to mine Bitcoin, Litecoin, BlackCoin, Namecoin, Feathercoin, Dogecoin, NautilusCoin, Darkcoin, and Vertcoin.
I think the term cheapest isn't valid as places like pbmining.com are a lot cheaper for mining BTC. (Right now CEX.io is slightly cheaper than Eobot.com) However it is very interesting and you can switch coins easily which is innovative. All in all Eobot does look very interesting.