This is the best one around
https://crypto-webminer.com/ they also have an app for iphones, and likely androids(I haven't looked).
I've seen a lot of them come and go,
https://cpufan.club used to be good, but it seems to be down.
There's always coinpot.co mining, but they're mining XMR and then giving you your desired coin, so I'm sure they're shaving some off of the top(why wouldn't they?). Also freebitco.in does mining, but I don't think mining bitcoin(or anything paying you out that infrequently is worth it). You need something that will pay out quickly(if it takes more than a week to get a payout, it loses its appeal in my experience).
CPU mining isn't really worth it, but I find it to be fun. In most cases its easier to download a miner and just mine the CPU coin directly,
https://cryptoknight.cc/ is a good resource for some CPU minable coins and zero fee pools, just pick the one you like and go to the get started page and see if you can figure out how to mine it on your PC.
Happy mining!