Flare is a collection of ActionScript 3 classes for building a wide variety of interactive visualizations. Written by Jeff Heer, flare can be used to build basic charts, complex animations, network diagrams, treemaps, and more. Flare is written in the ActionScript 3 programming language and can be used to build visualizations that run on the web in the Adobe Flash Player.
More information can be found on the official Flare site.
Prefuse is a set of software tools for creating rich interactive data visualizations. Written by Jeff Heer, this toolkit supports a rich set of features for data modeling, visualization, and interaction. It provides optimized data structures for tables, graphs, and trees, a host of layout and visual encoding techniques, and support for animation, dynamic queries, integrated search, and database connectivity.
Please visit the official Prefuse site for more information. The toolkit can be downloaded here.