The onramp Node module is used to establish connections, but after that it isn't necessary for communication between clients. The author has written up documentation with diagrams to explain how it works. Like other similar projects, the underlying technology is WebRTC, so it only works in Chrome or Firefox Nightly.
EasyWebWorker (GitHub: ramesaliyev / EasyWebWorker, License: MIT) by Rameş Aliyev is a wrapper for web workers which allows functions to be executed directly, and can execute global functions in the worker.
A fallback is provided for older browsers:
# Create web worker fallback if browser doesnt support Web Workers. if this.document isnt undefined and !window.Worker and !window._WorkerPrepared window.Worker = _WorkerFallback
_WorkerFallback class is provided, and uses
The source code is nicely commented if you want to look at what it does in more detail: easy-web-worker.coffee.
Jeremy found that OpenPGP.js is used by Mailvelope, which is a browser extension that brings OpenPGP to webmail services like Gmail. That means Mailvelope can encrypt messages without having to upload a private key to a server.