A practical introduction to D3.js, a JavaScript-based tool for creating web-based, interactive data visualizations.  D3 (Data-Driven Documents) is an extremely powerful tool, but it has a steep learning curve for people with little prior programming experience.  This tutorial is intended for beginners familiar with basic concepts of visualization, but with little or no experience with web development technologies such as HTML, CSS, JavaScript, and SVG.  We begin with a brief introduction to those technologies, and then quickly introduce D3, a JavaScript library for expressing data as visual elements in a web page.  Participants will learn how to load their own data sets into a page, bind the data to page elements, and then manipulate those elements based on data values and user input.  No programming experience required, although some familiarity with markup or scripting languages may be helpful.