I recently discovered what cloud mining was after using Cryptotab for the last couple weeks and now got started with MineEx. Cloud mining is when you mine a cryptocurrency using rented cloud computing power. There is no need for any physical rigs and whatnot. The best part is you don't need to have it open all the time! Just sign up and leave it alone to make money for you.

This website allows you a starting balance of 3000 GH/S without any deposits. You can also get a bonus up to 70Gh/s per hour. That's about $0.40 a month for life for doing absolutely nothing! (not including the bonuses)
Check out my other review of Cryptotab here. (Another cloud mining platform, among my favorites)