Web components bring a new way to modularize web applications through use of the shadow DOM. Polymer is a Google backed project that provides an easy web component implementation with a limited number of polyfills for older browsers lacking in support. Google also unveiled Material Design at Google I/O 2014, the visual language to be used in the upcoming version of Android. With it, they announced the availability of Polymer based implementations of Material Design.
One downside of Polymer at the moment is that each component imported into a page requires at least one additional server request, and if that component has dependencies it will make at least one additional server request per dependency. This can compound quickly and relatively simple pages will make an exceptionally high number of requests. This might be overcome with some type of build process that embeds referenced components directly onto your page before serving them to reduce the number of server calls.