Crypto Mining

https://www.coinimp.com/ has some possibilities maybe.

There’s an open source browser based miner available on github.

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Old but may still be valid.

webminepool.com has some kind of way we can get users to do mining on the site using their browsers.
ECMining is using the API and there seems to be a windows app too.

browsermine.com is another possibility, has an api. Info is on this page (may need to sign up to get that)