I will show you my most popular blockchain sites and share some slides from JKU Linz Blockchain course with you!
... most trusted source for data on the bitcoin blockchain:
Mempool Size,
Transactions per day,
Mining Revenue and Costs,
Most popular addresseshttps://blockchain.info/en/charts
Use case
Solidity
Try it yourself - learning how the blockchain works:
https://anders.com/blockchain/