The examples can be found under the examples directory. If you've downloaded a source-only distribution, in order to run them, you have to execute the jar target from the project's build script.
Interesting are the build.xml ant files and the artifacts declared in the artifacts.xml files.
Found under examples/simple. Contains three projects: car, engine and fuel. The car projects builds a car (was hard, heh?) which, of course, needs an engine. The engine runs with fuel :). So, when building the car project, the engine will be automatically built, which triggers the fuel project to be built.
The car project can be built by invoking ant car in the car directory.
Found under examples/dependencies. Contains a set of dependent projects and it's only purpose is to show how dependencies work. There are 6 projects, with their dependencies shown in the following image:
As you can see, building P1 requires P2, P3 and P4 to be built, which require P5 and P6. Three projects depend on P5 (P2, P3 and P6), which means that in the worst case P5 will be built 3 times. Fortunately, this is avoided and the build order will be P5, P2, P3, P6, P4, P1.
P1 can be built by invoking ant all in the p1 directory.