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Decentralized applications (dapps) | ethereum.org
DappRadar - Ranked list of blockchain dapps
The Defiant - Definitive Guide - Free, complete compendium
CoinGecko - How to DeFi - Paid, highly regarded book
DeFi Pulse - Projects & Total Value Locked (TVL)
Finematics - Guide to Decentralised Finance - Rich content, article + video per topic