From the incredible minds at Google :)
http://code.google.com/apis/chart/
This impressive little library lets you generate PNG chart files from a single URL request string. Since people typically need to pass lots and lots of data for charting, they came up with a really creative way to compress the values, and provide a javascript snippet for automating the process.
So the nifty chart you see to the right is a "hello world" app using their API. It ultimately comes down to a simple URL request of:
http://chart.apis.google.com/chart?cht=p3&chd=s:hW&chs=250x100&chl=Hello|World
Quite impressive and easy to use!
While this doesn't provide the stellar interactivity and depth of integration that Flex charts do, it certainly provides a way to do nice looking charts with a quick turn-around.
According to their docs, you can freely use this so long as you don't regularly exceed the 50,000 hits per day limit at which point they may block you. I think most of us will not be hitting it quite this much.
Some samples:
