Chartle is a new site (very early beta) designed to make online charts/graphs. While I don't think it is as dynamic or flashy as Rich Chart Live, I do think it has great potential to be a useful tool in education.
What separates Chartle from other graph designers is the different categories of charts that you can create. Not only can you do your standard bar/line/pie chart, but you can do: time lines, venn diagrams, maps, guages etc.
One of my favorites is the Radar Chart.
It's still to early to tell how well Chartle will stack up to their competetitors but from what I've seen here they are on the right track.
Check out Larry Ferlazzo's blog which introduced me to this application.
Give Chartle a try by clicking here.