What's cool: With Highcharts, users can mouse over items for more details; they can also click on items in the chart legend to turn them on and off. There are many different chart types available, from basic line, bar, column and area charts to zoomable time series; each comes with six stylesheet options. Little customization is needed to get a sleek-looking chart -- and charts will display on iOS and Android devices as well as on desktop browsers.
Drawbacks: Highcharts, like Google Maps, does have a distinctive look, so you may want to customize the Highcharts stylesheets so your visualizations don't look like numerous other Highcharts on the Web. While charts displayed fine for me on an Android phone, they weren't interactive (they were on an iPad).
Skill level: Intermediate to Expert.
Runs on: Web browsers
What it does: How often do you have data in one format -- while your application needs it in another? New York Times interactive graphics editor Shan Carter ran into this situation often enough that he coded a tool that converts comma- or tab-delimited data into nine different formats. It's available as either a service on the Web or an open source tool.
What's cool: Mr. Data Converter can generate XML, JSON, ASP/VBScript or basic HTML table formatting as well as arrays in PHP, Python (as a dictionary) and Ruby. It will even generate MySQL code to create a table (guessing at field formats based on the data) and insert your data. If your data is in an Excel spreadsheet, you don't need to save it as a CSV or TSV; you can just copy and paste it into the tool.
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