Adding another resource I use frequently:
https://cheats.rs/One part that I love especially about it is that it represents lifetimes [1] and memory layout [2] of data structures in graphical format. They're as invaluable as API references. I would love to see it included in other documentation as well.
[1] https://cheats.rs/#memory-lifetimes
[2] https://cheats.rs/#memory-layout