node.js – event-driven runtime environment for developing server-side applications . Allows you to develop in JS, and it’s quite fast. It also handles concurrent connections quite efficiently.
express.js – minimalist server-side web framework for node.js
angular.js – client-side, web applications framework, especially suitable for single-page applications
As for databases, MySQL seems to still be the default choice, by MongoDB and PostgreSQL are following closely.
Here’s an interesting post about the topic (though from 2014): Which Technologies Do Startups Use? An Exploration of AngelList Data