Blockchain

Dune Analytics

  • User-created dashboards
  • Extra useful for DeFi

Etherscan

  • ethereum focused
  • has wallet labels, transaction search, smart contracts

Google BigQuery

  • Supports most major chains including Bitcoin, Ethereum, Zcash, doge, etc
  • SQL syntax
  • very useful for graphs

CoinGecko

  • FREE API, with no keys