For Operators:

Official Channels:

For Delegators:

Official Sites:

Official Stake Pool School:

Gitbook 

IOHK Support:

Zendesk

Working on Testnet:

Cardano Testnets

Third party pool monitoring:

Adapools

Pooltool

Cardano Telegram

Cardano Forum

 Cardano Reddit

Cardano Foundation

Cardano YouTube

Cardano Twitter 

Official ADA Wallets:

Daedalus

Yoroi

Development Roadmap:

Cardano Roadmap

Official Cardano Explorer:

Cardano Explorer

Never Stop Learning