Cloud Mining Websites
There are a lot of scam cloud mining sites out there, so be careful and remember to look for proofs on the Verifications page.
Just a quick reminder: avoid any cloud mining site that promises or guarantees any kind of fixed daily profit. Mining is a randomized process, so it is impossible to guarantee anything.
Highly advertised site that offers 6x hashrate on all purchases
Dualmine is another platform that doesn't really send up any red flags for me as a scam. The 6x hashpower thing may just be a marketing ploy, as it seems that hashrate purchases tend to end up almost equal to those of other sites that don't make such claims, give or take. I have received payment from this site.
Reasonably profitable cloud mining site with a free trial period
I've looked at a lot of cloud mining websites. A LOT. Most of them are either scams that demand you pay a fee to withdraw your funds and never deliver the goods, or they are legitimate mining sites but their maintenance fees are so high you end up losing money daily. Hashshiny is different. Available via web browser and Android app, Hashshiny offers new users a free 300-Gh/s contract with an additional 3 Th/s for the first three days. Maintenance fees are based on your total hashrate in that mining protocol (which crypto you are mining) and are deducted from daily mining profits, meaning you don't have to pay anything out-of-pocket. Mining profits can also be automatically reinvested in additional hashrate, allowing users to increase their profits over time and earn even more without ever paying a thing. Mining continues even when you are not on the site/app. Finally, Hashshiny offers hashrate in several cryptocurrencies, allowing users to choose the most profitable coin to mine using their built-in calculator (calculated profits do not account for maintenance fees, so be mindful and do your own math, too).
Functionally free cross-chain PCX mining and staking
This one is unique in a lot of ways. For starters, you don't actually have to BUY mining power: it is assigned based on how much X-BTC (interchain Bitcoin) you hold. X-BTC is just BTC sent to your ChainX wallet using OP_RETURN. If you don't know what OP_RETURN is, don't worry, I didn't either. Despite being a giant pain in the ass to get started, ChainX presents a unique passive income opportunity in that the only thing you ever have to pay is very small transaction fees (but you will pay them for everything, even cancelling a purchase or sale). There is a requirement to claim mined PCX: you must have ten times the PCX claim amount in voting freeze. The good news? You earn on the PCX in voting freeze, too. There are no minimum withdrawal amounts for PCX mined, you can claim as soon as it would be profitable to do so ( though you must wait seven days between claims), provided you have enough PCX in voting freeze and enough left over to cover the transaction fee. These fees are adjustable (higher fee = faster transaction) and typically range from 0.0002 to 0.009 PCX, which translates to pennies at maximum.
P.S. There is no waiting period to claim interest from PCX staked in voting freeze.
Fair, feasible crypto mining for mobile users
It would take me a long time to explain this, so I'll just leave the link for their "white paper" here, https://minepi.com/white-paper. It's not hard to use the Pi app and you only have to come back once a day to restart the mining, so it certainly falls into what I see as ideal passive income. When you download the app using the link above, enter "strike8echo" without quotes as your invitation code.
Pi is not a fully operational blockchain yet. It currently has no value. As they point out, this was true of Bitcoin not so long ago.
Use protein folding simulation client to earn BAN
Have you ever wanted to do something practical to help fight and cure disease? This is your chance. Banano Miner uses the Folding@Home client (which you can download here) to help researchers perform protein folding simulations in order to develop treatments for various nasty, horrible, terrible, not good very bad illnesses. In exchange for your CPU and GPU power, you will be rewarded in points that will be exchanged at variable rates for Banano (BAN). It doesn't pay much, but you'll be doing good things for people who are suffering vicious maladies and praying daily for a solution.