Having just shipped a big “single-page app” project, I think it would be useful to list all of its dependencies among the current climate of dependency burnout in front-end land. Those were all very stable and easy to combine.

• React – I’m not doing any JS front-end without React these days. The development experience is amazing, and they have done a terrific job at being highly stable over time. It’s always a pleasure to upgrade the React version.
• Redux – Very stable and reliable, high learning curve but high reward too
• D3 (v3) – One of my favorite tools. Can’t wait for v4 to be out, the main issue with D3 as it stands now is that I’m only using a fifth of its features but still shipping it all in my JS
• Springload’s reusable components react-simpler-select, react-svg-icon, react-accessible-modal Because for UI elements you likely want to have your own touch.
• Flexbox – Such a pleasure to build layouts with this, if browser support isn’t too advanced (no IE10 and below)
• react-autosuggest – A nice UI component that took care of what’s hard - keyboard interactions and accessibility
• react-router – Probably the least stable of all of those building blocks, but they have done a better job at this since version 2.
• Browserify + gulp builds – Webpack might be better, but its documentation / ease of use is not.

Other goodies:

• copy-to-clipboard
• Client-side search with elasticlunr – Like lunr.js but better.
• sessionStorage caching
• performance tracking
• autotrack analytics - Another one of my favorites, more recent.
• babel-plugin-lodash for smaller builds
• npm shrinkwrap – Finally!
• Integration tests with Nightmare
• SVG+CSS export as SVG/PNG – The more R&D part of this project, which turned out to work quite well