Maps petitions from the We the People petition website out of the White House - https://petitions.whitehouse.gov/.
This code queries the We the People API with a particular petition id and then visualizes the signatures on either a zoomable or a state-based map. It's all javascript and client-side technologies which means you don't have to run any fancy PHPs or Rubies or server-side stuff.
See it in action here: http://kanarinka.brownbag.me/petitionmap/index.html
Please feel free to download and use! Any questions about usage, drop me a line dignazio@mit.edu.