One of the best places to find stuff like that is the apache.org website. Many of the projects - both simple and complex - are built with Maven. Which is only fair, since Maven itself is an apache.org project. Look at some of the simpler libraries for basic project design examples.
One notable exception is Apache Tomcat. It's not what I'd call a small, simple project, but they don't care for Maven, so Tomcat is built via Ant.
CodeHaus is another place worth looking into.
One thing you might want to do is pick your favorite Java open-source product and pull the source code for it. Chances are almost 100% that either Maven or Ant is being used to build it, and you may find it easier to understand a project if you are already familiar with how it works.
Customer surveys are for companies who didn't pay proper attention to begin with.