WebAssembly is gaining traction for various applications out-of-browser - with blockchain being one of them. This brief article neatly summarised the significance of two technologies, WebAssembly and Blockchain, and a concept, Reputation. When all three combine, distributed application could really take off.
The Rust community has some of the most advanced WebAssembly tooling, thanks to the team at Mozilla. This tutorial gives a thorough introduction to the tools and ecosystem, from first steps to publishing your finished module.
Talking of Mozilla, this blog post and video announces some further tooling improvements. Currently debugging support for WebAssembly, i.e. being able to set a breakpoint against a program running on the WebAssembly VM and step through execution in the source language (i.e. Rust, AssemblyScript, C++) is limited. Mozilla are working hard to solve this problem.