The Gliffy PHP SDK by Gliffy allows API interaction, providing drawing features such as diagrams and flowcharts that developers can integrate into visualization applications. Resources include installation and configuration. To use the SDK, experiment creating a new diagram in PNG format.
Chart APIs are useful and popular, and Google knows how to do them well, so they're continuously adding more features and options for customization to their Visualization API. The Google Code Blog recently highlighted a few of the newest features.
Practical Management Solutions and Insights (PMSI) has launched an open-source API project for business analytics: dimple. Dimple aims to open up the flexibility and power of d3 to analysts. With little d3 knowledge needed, the dimple API gives analysts access to the tools capable of creating dynamic graphical representations of datasets.