Lucia's list of awesome Apache Kafka resources. Feel free to PR and add your own.
Apache Kafka 101 Tim Berglund leads Confluent's course introducing the basic concepts behind Apache Kafka.
Apache Kafka Versions - maintains a list versions of major open-source dependencies of Apache Kafka releases.
Confluent Developer - a matrix of resources, including courses and tutorials, owned and maintained by Confluent.
Confluent Resources - Confluent Resources Search is a great way to find tons of content. For example, search for "kafka summit" to find breakout and lightning sessions.
Designing Event-Driven Systems - Author Ben Stopford explains how service-based architectures and stream processing tools such as Apache Kafka can help you build business-critical systems.
Dev Local - A container based ecosystem for exploring real-time technologies, with Apache Kafka at the core. Check out Dev Local Demos as the companion repository that has real-time examples using the dev-local ecosystem.
Gently Down the Stream - A Gentle Introduction to Apache Kafka
I <3 Logs - Based on his popular blog posts, LinkedIn principal engineer Jay Kreps shows you how logs work in distributed systems, and then delivers practical applications of these concepts in a variety of common uses—data integration, enterprise architecture, real-time stream processing, data system design, and abstract computing models.
Kafka the Definitive Guide - Kafka The Definitive Guide Real-Time Data and Stream Processing at Scale, 2nd Edition.
Streaming Audio Podcast - Join Kris Jenkins and guests from the community as they discuss the latest Apache Kafka® news, use cases, and trends spanning the topics of data streaming, microservices, modern IT architectures, and the cloud.
Apache KIP - Kafka Improvement Proposal - This is the best source of documentation for the Apache Kafka project. Why's, what's and how's are covered in each document. Be sure to pay attention to "Rejected alternatives".