Noodle is a simple graphing application. It's developed for displaying graphs of service response times, but you should be able to graph other kinds of time-scale data using it.
Noodle is currently pre-alpha; you can't do much other than look at some really basic, incomplete graphs.
Noodle is implemented using Python, GTK, and Cairo. Currently you need GTK installed to do anything interesting with it, but the graphing portion of the code doesn't refer to GTK directly, so it should be possible to generate static graphs (a la rrdtool) in the future.
Noodle is free software, licensed under the GPL version 3. Consult the LICENSE file for the copyright and licensing details.