At Freakalytics, we've used the D3 data visualization library on several client projects and have been impressed with the nearly infinite set of graphing, charting and mapping possibilities. Unfortunately, we were less impressed with the high learning curve, level of effort and complexity involved in developing and customizing the desired visualizations.
Perhaps you have seen D3 in the New York Times? D3 examples like those in the New York Times are typically made by teams with expertise in D3 and related web technologies. Now, forward-leaning visual analytics companies like Qlik are opening their API to work in harmony with the wide range of D3 visualizations.
Now, the really good news! An open source effort at the Data Lab of The University of Washington has created Lyra, a point-and-click editor for creating D3 visualizations. We've used it and were impressed with it, so we wanted to share it with you as a learning resource or even a productivity tool. Keep in mind that Lyra is still experimental and requires some effort on your part to properly embed it in your work. The UW Data Labs has created some nice videos, tutorials, examples, a Wiki and a discussion group for your learning benefit.
One of the examples posted by the Data Lab is a classic data visualization piece, Napoleon's March.