The Javascript libraries I explored for gauge charts are :
- Jqplot Provide simple meter in non attractive manner
- Flot Better the Jqplot but but still less professional
- Google Chart Professional output and it is also generating cross browser compatible HTML/SVG chart like d3js
- Fusion Chart(Commercial) professional output but not free
You can find below chart example from my github account. I took and extend example from following example https://gist.github.com/tomerd/1499279