I have made money leasing rigs, but thats mainly because I have my own mining hardware too so spotted a couple of opportunities like CINNI before most people did. Usually people leasing their rigs do so at a rate slightly higher than they think they will be getting mining on their usual pool, so its always going to be hard to beat them.
People will recommend various cloud hashing services, I myself have a referral link for Scrypt.cc in my signature below so its pretty obvious what my preference is
Trying to be unbiased though, and having posted in several threads like this, I will say its not just about the cheapest hash rate or highest return, you need to look at all the angles. I've tried to simplify it into a few questions:
1) SHA256 or Scrypt? The latter is more profitable but potentially less stable, with a lot of new ASICs due to be released in the coming months. I'll assume not SHA256 as this is the altcoin forum
2) Are you looking for a longterm investment into mining (6+ months) where you manage what coins you are mining? If so consider buying hosted hardware from somewhere like gawminers.com or Farmshares, but you really need at least
BTC0.5 minimum.
3) Want a shorter term option that you can get out of if you need? Cloud mining exchanges like Scryptmining.com and Scrypt.cc have exchanges where you can buy & sell KHS, and you earn mining income whilst you hold KHS. Over time the value of your KHS is likely to decrease but the mining income should more than make up for it. You don't get any control over the coins your KHS mine though, you're relying on the "experts" who run the service to make those decisions and return the best rewards for you.
4) When you've narrowed it down to a couple of sites do a bit more research, don't rely on "reward calculators" on the website, see if you can find some user reports. Also remember you don't have to put all your money in one place, consider splitting it across a couple of sites if possible - it will reduce the risk of losing it all and also allow you to compare performance.
5) Pay attention to crypto news and developments, how will they affect your chosen investment? Is a new Scrypt ASIC coming on the market going to render all other Scrypt miners obsolete, or is your cloud mining service changing their fees soon which might cause the price per KHS to halve?
6) Keep records of your investments & returns so you can track net value over time, setup a Google spreadsheet and remember to update it! If your net worth is consistently decreasing or your ROI keeps dropping then ask yourself if you should maybe do something else?