Udemy offers the Complete Bitcoin Course bundled with 0.001 Bitcoins for $15. Coupon code "JAN2202" drops it to $10. Adding in the value of the Bitcoins (they're worth about 89 cents), that's $34 off and tied with our mention from two weeks ago as the lowest total price we could find. It teaches you the basics behind this crypto-currency.
The planet will thank you, your local (overwhelmed) landfill will thank you. Even your budget will thank you.