Recs.
Updated
Smashing is a fork of Dashing (which is no longer maintained), a Sinatra based framework that lets you build beautiful dashboards.
SpecsUpdate
Pros
Pro Huge library of widgets available
Smashing has a huge library of user contributed widgets available.
Pro Comprehensive docs with many examples
The wiki on Smashing's Github page includes many examples and how-to's, e.g. How-to: Add-authentication.
Pro Write custom widgets in HTML/ERB, SCSS, and CoffeeScript
Smashing is based on Ruby / Sinatra. Its widgets are essentially a collection of Ruby erb templates for layout, SCSS for styling, and CoffeeScript for data polling/interactivity. If you have worked with Rails, Sinatra, or any other Ruby-based web framework and CoffeeScript, customizing widgets shouldn't be hard.
Pro Easy deployments to Heroku
You can deploy Smashing to Heroku easily with a few commands, as documented on How to: Deploy to Heroku of their Github's wiki.
Pro Can feed data to widgets directly through Ruby
You can feed data to widgets directly from a Ruby script/app. Smashing uses job scheduling (rufus-scheduler) to update widgets, and it also provides a command to generate a template for jobs: dashing generate job sample_job
. This is convenient if you have an application written in Ruby, or interacts with your data source using Ruby.