I am willing to bet that everyone here on this site likes cryptocurrencies and also likes earning them for free. If not please let me know :)
With that in mind let's take a look at everything I invest my time and energy into to earn free Cryptocurrency.
Brave Browser and BAT:
This isn't necessarily passive but it's darn close. For those of you who do not know, the Brave Browser is a Chromium based Browser that blocks ads by default. In exchange for that it will show you notifications for ads. If you choose to click on the notifications you earn 0.5 BAT. It's free money and if you are normally online throughout the day it makes no sense not to use Brave.

Brave also announced this morning that they are going to push out Sponsored Images. Which means on the New Tab screen instead of their rotating pictures they normally have they will sell the space to companies to display an image and their logo. It is very non intrusive and will also earn you BAT for viewing the image. What I love about Brave is that everything is opt-in. So if you want to see ads to earn BAT you have to opt-in. The built in ad blocker is not opt-in and is on for everyone.

Tezos Staking:
There are multiple sites where you can do this but I will talk about Coinbase because that is where I have my coins. On Coinbase you can opt-in to Stake your Tezos (XTZ). All you need is more than 1 XTZ to stake and when you do and hold it in your account for at least 35-40 days you will start to earn 5.44% apr on that amount. It pays out every 3 days back to your Coinbase account and the interest is all compounded so then you earn that 5.44% on your 1 XTZ plus whatever you get each 3 days.

You can also stake Dash, NEO, OKCash, BNB, VET among others.
CryptoTab Browser:
CryptoTab Browser is a mining browser. It mines XMR while you have it open. Think about it a mining software with a browser built into it. The other feature that it enables is a Referral Scheme. If you refer people and they use the browser you get a bonus amount of mined currency. So for people you directly invite you get 15%. People that they invite you get 10% and so on until the 10th level below you. If you put the initial work into this you could get a pretty penny doing this and never have to do anything after it is already setup. Just leave the browser open and if everyone else does as well everyone makes BTC. CryptoTab mines XMR but pays out in BTC and it pays out very quickly. I have seen people purchasing Adf.ly traffic to push out their link and they have earn thousands of dollars. That is not for everyone but it definitely is possible.

Any Mining Software:
If you put in the time to mine a coin then you will just earn that coin over time. It all depends on the coin and the pool but it can be a very easy method to earn a return but the returns are not always that great unless you have a beefy computer. Mining solo is usually not worth it. So finding the right Pool to join it beneficial. I am not going to list every Cryptocurrency that can be mined because there are too many to list here.

I will also list some semi-passive earning options
Mobile Mining:
This is as close to passive mining I think that you can get because it only requires you to "check in" from time to time to keep mining. Most of these are not actual mining on your phone but what I call Cloud mining. You still get the return in currency but you don’t need any special hardware. A few examples are Electroneum which you only need to check in once every 7 days. And then there is Pi which you need to check in every day. I do both of those and love them.


BlockChain Blogs:
What I mean by BlockChain Blogs is websites like Publish0x. It can be a news site, blog site or a combination of the two where you can earn Cryptocurrency for interacting on them. For example on Publish0x you need to actually tip people to earn Crypto or write articles and receive tips to earn it. It writing is something you love to do and can write well written articles about topics people care about you can earn a nice amount of Cryptocurrency. If you are just a ready and tip regularly you can also earn a small chunk of change here.
There are other sites as well like Uptrennd and Read.Cash that are very similar.

BlockChain Games:
I include these because if you are going to play mobile games or web based games you should just play ones that can earn your cryptocurrency. Kill two birds with 1 stone. Some of them are more in depth than other and the amount you earn varies greatly on the game and how often you play. Here are some examples of Games that you can play to earn Cryptocurrency:
Those are just a few games and there are plenty more!