tgif is a vector-based drawing tool, with the additional benefit of being sort of a web-browser. That is, you can fetch drawings from a web server with it, and you can make objects in your picture into hotlinks to other parts of the drawing, or to other drawings accessible via HTTP.
JpGraph is an OO graph drawing library for PHP 5.1 and above. Highlights of the available features are: multiple scale types; anti-aliasing of lines; color-gradient fills; support for GIF, JPEG, and PNG formats; and support for multiple Y axes. Many plot types are supported, such as pie-charts, lineplots, bar plots, impulse plots, polar plots, error plots, contour plots, matrix plots, gantt charts, and many more. The pro-version also contains extensive 1D and 2D barcode support. The documentation is extensive and is over 700 pages.
Engauge Digitizer is digitizing software that converts an image showing a graph or map into numbers. The image file can come from a scanner, digital camera, or screenshot. The numbers can be read on the screen, and written or copied to a spreadsheet. Highlights for beginners include an intuitive interface and extensive context-sensitive documentation. Highlights for experts include compensation for image distortion, cartesian and polar coordinates, linear and logarithmic coordinates, automatic scanning, graphical previews, and browser help.
ResCafé is a Swing-based Java utility for reading and extracting resources such as ICONs and MENUs from the Resource Forks of Macintosh files. In particular, it allows Linux users to use nifty Mac-only icons with their favorite desktop, e.g., KDE. It is somewhat similar to ResEdit on MacOS except that it is not an editor; it operates on files in a read-only fashion. The various resource types are parsed by auto-detected plugin handler classes.