A more complete and up-to-date list of resources can be found at the reactivex.io site

Introducing Reactive Programming

• Introduction to Rx: a free, on-line book by Lee Campbell (1.x)
• The introduction to Reactive Programming you've been missing by Andre Staltz
• Mastering Observables from the Couchbase documentation (1.x)
• Reactive Programming in Java 8 With RxJava, a course designed by Russell Elledge (1.x)
• 33rd Degree Reactive Java by Tomasz Kowalczewski (1.x)
• What Every Hipster Should Know About Functional Reactive Programming - Bodil Stokke demos the creation of interactive game mechanics in RxJS
• Your Mouse is a Database by Erik Meijer
• A Playful Introduction to Rx a video lecture by Erik Meijer
• Wikipedia: Reactive Programming and Functional Reactive Programming
• What is Reactive Programming? a video presentation by Jafar Husain.
• 2 minute introduction to Rx by André Staltz
• StackOverflow: What is (functional) reactive programming?
• The Reactive Manifesto
• Grokking RxJava, Part 1: The Basics, Part 2: Operator, Operator, Part 3: Reactive with Benefits, Part 4: Reactive Android - published in Sep/Oct 2014 by Daniel Lew (1.x)
• Reactive Programming on Android with RxJava, a free e-book by Chris Arriola and Angus Huang.

How Netflix Is Using RxJava

• LambdaJam Chicago 2013: Functional Reactive Programming in the Netflix API by Ben Christensen (1.x)
• QCon London 2013 presentation: Functional Reactive Programming in the Netflix API and a related interview with Ben Christensen (1.x)
• Functional Reactive in the Netflix API with RxJava by Ben Christensen and Jafar Husain (1.x)
• Optimizing the Netflix API by Ben Christensen (1.x)
• Reactive Programming at Netflix by Jafar Husain (1.x)

RxScala

• RxJava: Reactive Extensions in Scala: video of Ben Christensen and Matt Jacobs presenting at SF Scala (1.x)

Rx.NET

• rx.codeplex.com
• Rx Design Guidelines (PDF)
• Channel 9 MSDN videos on Reactive Extensions
• Beginner’s Guide to the Reactive Extensions
• Rx Is now Open Source by Scott Hanselman
• Rx Workshop: Observables vs. Events
• Rx Workshop: Unified Programming Model
• MSDN Rx forum

RxJS

• the RxJS github site
• An interactive tutorial: Functional Programming in Javascript and an accompanying lecture (video) by Jafar Husain
• Netflix JavaScript Talks - Async JavaScript with Reactive Extensions video of a talk by Jafar Husain about the Rx way of programming
• RxJS, an on-line book by @xgrommx
• Journey from procedural to reactive Javascript with stops by Gleb Bahmutov

RxAndroid

• FRP on Android - publish in Jan 2014 by Yaroslav Heriatovych (1.x)
• RxAndroid Github page (2.x)
• RxAndroid basics (1.x & 2.x)
• RxJava and RxAndroid on AndroidHive (1.x & 2.x)
• Reactive Programming with RxAndroid in Kotlin: An Introduction (2.x)
• Difference between RxJava and RxAndroid (2.x)
• Reactive programming with RxAndroid (1.x)
• RxJava - Vogella.com (2.x)
• Funcitional reactive Android (1.x)
• Reactive Programming with RxAndroid and Kotlin

Miscellany

• RxJava Observables and Akka Actors by Anton Kropp (1.x & 2.x)
• Vert.x and RxJava by @petermd (1.x)
• RxJava in Different Flavours of Java: Java 7 and Java 8 implementations of the same code (1.x)