Decentralized Finance (DeFi) — ethereum.org
Ethereum Foundation
The Ethereum Foundation's own overview of decentralized finance, covering lending pools, flash loans, decentralized exchanges, stablecoins and tokenized assets. Gives a newcomer accurate vocabulary and correct mental models before tackling protocol documentation or research papers.
More resources on DeFi (Decentralized Finance)
Advanced Smart Contract Development with Foundry — DeFi & Stablecoin Module
A free hands-on curriculum whose DeFi module builds an overcollateralized stablecoin end to end: collateral deposits, health factor calculation, liquidation logic, Chainlink price feeds and stale-oracle handling, verified with fuzz and invariant testing.
Uniswap V3 Development Book
An open-source guide to rebuilding Uniswap V3 from scratch in Solidity with Foundry. Working through it, the constant-product invariant, concentrated liquidity, tick math, swap routing and fee accounting stop being a black box.
SoK: Decentralized Finance (DeFi)
A systematization of knowledge decomposing the DeFi ecosystem into its primitives, protocol types and security properties. After reading it you can classify any protocol by underlying mechanism and reason separately about its technical and economic attack surface.
Decentralized Finance MOOC (Berkeley / Stanford / Imperial / UIUC)
A university lecture series covering DeFi primitives end to end: automated market makers, lending and debt models, stablecoins, oracles, derivatives, MEV, historical attacks and on-chain governance. Recorded lectures and slide decks are freely available.