It wasn't immediately clear if JSFlot handles radar charts however flotr does. flotr is based on the prototype library rather than jquery
so you might need to use jQuery.noConflict() to get it to work.
Alternatively just google jquery+charts+plugin and take your pick. See also http://www.jqchart.com/samples/RadarPolarCharts/RadarLineChart.
If you need to get data from the server you could use a4j:jsFunction with the data= attribute, perhaps in conjunction with a JSON library.