Figure 1. Creating Charts with Bluff (courtesy of Bluff Homepage)
As I mentioned, one of Bluff's interesting features is the ability to create and reuse themes rather than continuously recreate design attributes. For instance, Figure 1 was themed using the 37Signals theme, whereas Figure 2 is themed using the Odeo theme.
Figure 2. Creating a Themed Chart with Bluff (courtesy of Bluff API documentation)
From an interactivity perspective, dygraphs is perhaps the solution offering the most impressive array of features right out of the box. It is capable of producing highly interactive graphs that even allow the user to selectively choose and zoom in on desired sections. If you're looking for a solution that can really draw the user into the presentation, dygraphs is certainly worth investigating.
Figure 3. Charting Temperatures in NYC and San Francisco (courtesy of dygraphs home page)
Although free for personal use, commercial users must buy a license in order to use the Emprise library. Costs are minimal, however, starting at just $100 for a license allowing use on a single Web site.
4. FlotFlot is another charting solution that has invested significantly in interactive features such as zooming and mouse tracking. Although the example found on the Flot homepage seems to indicate Flot's tendency to be used in scientific applications (see Figure 4), Flot is actually being used for a wildly diverse array of purposes. Just last month Spain-based developer Michael Freeman released a particularly interesting Flot-driven application called Google Analytics Evolution, which uses the Google Analytics API in conjunction with Flot to produce an amazing new way to examine your Google analytics data.
Figure 4. Mouse-tracking with Flot (courtesy of Flot documentation)
5. Google Chart Tools
Of all the solutions presented in this article, Google Chart Tools is the undisputed heavyweight in terms of support for nearly every imaginable chart type, whether it's a simple pie chart or something far more complex, such as a country-based intensity map. It even supports rather unconventional charting solutions such as the gauge-based chart presented in Figure 5.
Figure 5. Creating a Gauge-based Chart (courtesy of Google Chart Tools documentation)
Google Chart Tools actually brings together two of Google's previously separate charting solutions: the Google Visualization API and the Google Chart API. These solutions are representative of the entire charting gamut, simple enough for users with no coding experience to use by embedding Google-generated code into their Web sites, and simultaneously complex enough to allow experienced developers to create entirely new chart types such as the DrasticTreemap.
If you want to learn more about what Google Chart Tools has to offer without downloading the library and wading through the API, check out the Google Code Visualization Playground, which allows you to create charts using a GUI-based interface.