Ask HN: Best graphing/widget libraries for dashboards?

http://www.highcharts.com is amazing and used across a lot of the US's biggest investment banks. Creative commons version available or per user/organizational licenses.

http://d3js.org though I have a particular soft spot for.

I second HighchartsJS. The learning curve was minimal (imho) because of the massive amount of examples with jsfiddle links to tweak the settings: http://www.highcharts.com/demo/

Their API reference is pretty good as well: http://api.highcharts.com/highcharts

For our dashboards and most reports we now use a combination of custom Highcharts charts and standard widgets available at Geckoboard.

http://grafana.org/ opensource and free

I usually go for DyGraphs. Simple + easy to use + lots of configuration + excellent docs