VennGenerator is a simple Java program for creating Venn diagrams.

You can specify the area, axis ratio, angle, and color for each
oval, and then drag the ovals into position to get the desired
amount of overlap.  To help you achieve accurate intersections,
the program reports the areas of all component regions in a list.
These have slight variations due to rounding, but are still much
more precise than just placing the ovals by eye.

To save the diagram, use your operating system's "screenshot",
"print screen", or "grab" facility to save an image of the window
to a file, then crop it as desired and add labels, etc. using
graphics-editing software.  (Be careful with rescaling and format
conversions, as these may degrade the image.)

An "Export" button displays the positions and other settings for
all of your ovals, so you can copy and paste this information
into a text file for future reference, or use it to re-create the
diagram in another application.  Note that in Java the X coordinate
increases from left to right as usual, but the Y coordinate
increases downward, from top to bottom; thus the origin is in the
upper left corner of the panel.

To install, just copy the venngen.jar file to a local directory
(no need to unzip it).  Then to run it, use a command like this:

  java -jar ~/.../venngen.jar

You will need Java 1.3 or higher; Sun's version is recommended.