Polybar aims to help users build beautiful and highly customizable status bars for their desktop environment, without the need of having a black belt in shell scripting. It has built-in functionality to display information about the most commonly used services. Has a large number of built-in widgets for many different facets of system status.

In the AUR.

A Mediawiki extension that allows the creation of raw HTML snippets that can be used in wiki pages that do interesting and helpful things. Implemented by creating a namespace called Widget, into which new wiki pages containing the widget code in question can be written like any other wiki page. The API is documented on this page.

A module for python that abstracts away the annoying parts of ncurses and lets you build console-based user-interfaces. Has a collection of widgets that can be assembled into larger projects. Also has graph, text editing, file browsing, subprocess initiation and monitoring, color palettes, sub-windows, and font manipulation primitives.