I don't really know of any good general resources; they're often pegged to a specific programming language because the ways in which you have to achieve real-time compatibility differ depending on how the language and its runtime behave. We do all of our work in Java, which is definitely not a great candidate for real-time in most cases, so a lot of what I've learned about real-time programming has come from having to wrangle the JVM in to doing what we need it to do.

The fields that come to mind when I think of real-time outside of HFT, though, are control systems and digital signal processing (DSP). While DSP doesn't necessarily need to be real-time if you're doing it for analysis, doing DSP live definitely requires real-time programming knowledge since signals are often expressed in the time domain and any delay in computation of a discrete element will propagate in how the signal is interpreted. For example, if the signal you're processing is a sound signal (like music), and you are doing software-based DSP on the signal before it reaches the playback device, it better be real-time or any delay spikes will ruin the playback. This is why OS X is so popular with the music industry and especially DJ's; the Mach kernel has really good real-time support and a pretty good real-time software based DSP library for building apps.

You might be interested that Aicas is driving the new real time specification for Java.

https://oracleus.activeevents.com/2014/connect/fileDownload/...

We have some contacts at Aicas, and we've used both the original RTSJ in the past as well as evaluating Jamaica. Myself and a colleague recently attended JTRES and spoke to Dr. Hunt about where Aicas fell short for our specific use case, and in the very near term it won't be usable for us. We're looking in to re-evaluating it around summertime.

This is one of the primary use cases for Ada, so asking this question on /r/ada or the like would be a good start.

Also check out Real-Time Java: https://en.wikipedia.org/wiki/Real_time_Java