Hands-On Data Visualization, by Jack Dougherty and Ilya Ilyankou, is an open-access book geared for beginners. The book starts with spreadsheets, and then walks you through some of the more high-level JavaScript libraries to put things online relatively quickly. If you don’t have programming experience but want to kick the tires, it’s probably worth saving this for later.
You can also grab a physical copy.
Visualize This: The FlowingData Guide to Design, Visualization, and Statistics
