https://www.sparkfun.com/ This is pretty much The One of all the component sites. It is usually where I go to look up components to see their descriptions or for more information and links. They often have tutorials or datasheets and it is a great place to see what components are even available because chances are Sparkfun has it first and then the other distributors get it from them. USA based site so if you’re in the UK like me be aware of hefty duty fees! Ouch.