What’s New, Upgrade Notes, Supported Versions, and other topics, independent of release cadence, are maintained externally on the project’s Github Wiki.

Overview

history, design philosophy, feedback, getting started.
Core

IoC Container, Events, Resources, i18n, Validation, Data Binding, Type Conversion, SpEL, AOP.
Testing

Mock Objects, TestContext Framework, Spring MVC Test, WebTestClient.
Data Access

Transactions, DAO Support, JDBC, O/R Mapping, XML Marshalling.
Web Servlet

Spring MVC, WebSocket, SockJS, STOMP Messaging.
Web Reactive

Spring WebFlux, WebClient, WebSocket.
Integration

Remoting, JMS, JCA, JMX, Email, Tasks, Scheduling, Caching.
Languages

Kotlin, Groovy, Dynamic Languages.