- Geckoboard - http://www.geckoboard.com/ - Slick data dashboards.
- Leftronic - https://www.leftronic.com/ - Similar, doesn't seem quite as organised looking
- Dashing - http://shopify.github.io/dashing/ - Simple metric dashboards by Shopify. Widget list
- HighCharts - http://www.highcharts.com/ Not very inspiring but very widely used & performant
- Google Charts - https://developers.google.com/chart/ Again, not very inspiring but can be customised
- Flot - http://www.flotcharts.org/ Gorgeous slick HTML5 graphs
- RGraph - http://www.rgraph.net/ - More HTML5 based graphs.
- RaphaelJS - http://raphaeljs.com/ - Not graphs, just a nice JS framework for manipulating HTML5 canvas.
- D3.js - http://d3js.org/ - Another nice canvas JS library
- Cubism JS - http://square.github.io/cubism/ - Square use this for some nice basic aggregated+comparative graphs
- Rickshaw - http://code.shutterstock.com/rickshaw/examples/extensions.html - Awesome streaming graphs
- NewRelic - http://newrelic.com/enterprise - App monitoring
- Sentry - https://getsentry.com/welcome/
- Graphite - http://graphite.readthedocs.org/en/1.0/overview.html
- Splunk - http://www.splunk.com/ - Browsing huge log datasets