Update: Summer Sale 2015, Part II!
Hashflare.io (supported by hardware manufacturer Hashcoins.com) offers a cheap start into cloud mining:
Currently Hashflare.io offers a summer sale: 10% discount for orders of 250 GH/s mining power (HF15SMMR5P2) and even an incredible 20% discount for orders of 2.500 GH/s with the voucher code (HF15SMMR20P2). Of course, the risk is as everything in life with the buyer. I decline all responsibility.
The Hashflare.io Summer Sale offers a quick and easy introduction to cloud mining. Get it now!