Google Chart API
I’ve not had a chance to try these out with an actual project yet, but the Google Chart API seems to be a decent way to get Tufte® compliant chart images using simple web requests. Just pack the info for the chart’s appearance and data into a specially crafted URL and you’re set.
It’s a nice idea for a service, and I also appreciate that Google has kept it simple, rather than implementing it through a series of obfuscated and strangely-crafted embedded JavaScript (like, say, Google maps or their newer search APIs after discontinuing the SOAP protocol).