[egor83]

I see http://www.highcharts.com/ come up now and then.

D3.js is a great tool for data visualization, but that might be an overkill if your needs are simple.

[S4M]

There is also dimple.js [0] that is built on top of d3 and very easy to use, or TauChart [0], that was submitted 3 weeks ago on HN. I never used TauChart but I will give it a shot next time I need to do some graph because it looks really great.

[0] http://dimplejs.org/

[1] http://blog.taucharts.com/taucharts-data-focused-charting-li...