I’d be very surprised if the developers of Timetric didn’t work straight out of Richardson and Ruby’s RESTful Web Services just as many of us did.  They offer a webservice that lets you upload time-series data in a file, creating a resource from it with an overloaded POST in place of the expected PUT.   On success, a 303 is returned with the URI of your new resource in the Location header.   Do a GET on it, and you see it beautifully plotted, get an embeddable URL for the graph, and even get your original data back.   Use POST to add to or change your data, and DELETE to remove your resource.  They adhere to R&R’s gold-standard as closely as could be expected.

Editorializing for a moment, the best reason to check them out is to have a look at their API documentation.  It is the paragon of elegant simplicity and I only wish the Unix man pages were as easily digested.  Requiring neither flash nor javascript, they render as sensibly on my Treo as they do on my twin 17″ monitors.