Unfortunately there aren't as many good electronics resources online as you can find for software.

"Lessons in Electric Circuits" by Tony R. Kuphaldt is a pretty good introduction to the basics, you can find an improved version online: http://www.allaboutcircuits.com/textbook/

The most popular book is probably "The Art of Electronics", it's pricey but well worth it if you're serious: https://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521...

Check the usual suspects for communities, e.g. Reddit (/r/electronics, /r/AskElectronics) and StackExchange.