Reactive programming is seeing a lot of interest these days. Reactive Extensions is one way of adressing the problems of asynchronous, event-driven programming. Originally developed in Microsoft, it is one of the libraries that they have open sourced and it is now quite popular also outside of MS. Netflix is now the poster boy for Reactive Extension and they run the Java version.
I have put together some resources for people wanting to have a look at it.
Here is a short interview with Erik Meijer, creator of LINQ and Rx.NET, where he explains Reactive Extensions in less than 15 minutes. High ROI!
This is the homepage of all the variants of reactive extensions. It is actively developed and now is nicely branded. Their resources page is extensive and worth a look : http://reactivex.io/tutorials.html
This excellent blog post is what made reactive programming start to click for me. This is concrete, clear and well written.
Netflix' online tutorial for Rx.js. This is very good. It takes a while to get through the excercises where you implement map, filter, etc. but after that it is a very good intro to practical use of Rx. Highly recommended!
A series of blog posts turned into e-book that gives an intro to Rx.NET. If you're on the .NET platform this might be just what you need.
A couple of presentations by people on Netflix about how they are using Rx.Java. Jafar Husain and Ben Christensen are very good presenters and give a good overview.
A blog series about Rx.Java on Android but it explains Rx generally. Well written and helps you grok Rx easier.
There was a mini conference about reactive programming in London called React 2014. For all of us that could not attend the presentations are on YouTube.