The fine folks at Google have introduced a really simple API for generating charts:
This URL:
http://chart.apis.google.com/chart?cht=p3&chd=s:hW&chs=250x100&chl=Hello|WorldCreates this image:
That’s it – no state, no calls, just send your data in an http request and get a png image graph back. Embed the request in an img tag and you’re done. We currently support line charts, bar charts, pie charts, scatter plots, and sparklines.
If you’re not familiar with sparklines, they’re simply little in-line charts. Tufte discusses them at length in his Beautiful Evidence.