Besides Polymer, other popular web component platforms include X-Tag and Bosonic. X-Tag is a small library made by Mozilla that brings web components’ custom element capabilities to all modern browsers. It lets you easily create elements to encapsulate common behavior or use existing custom elements to quickly get the behavior you’re looking for. X-Tag is actually built on top of Polymer polyfills, and includes some cool built components like Panel (mimics iFrame), Modal, and Map (Leaflet). Bosonic follows the web components spec closely and includes lots of components: collapsible, sortable, datepicker, dropdown, datalist, tooltip, accordion, draggable, toggle-button, tabs, autocomplete, resizer, dialog, selectable, and flash message.
Web Components are not fully supported on Safari and Internet Explorer yet; however with Polymer, web components are supported in the two latest versions of all modern browsers except for IE8, IE9, and Android. Chrome Canary is currently the best browser for use with web components.