XRadar seems to be an interesting code analysis tool. It combines tools like JDepend, PMD and Checkstyle to build one big project report. It's different from Maven, as it will actually combine data from the different tools to come up with a combined project analysis. Reports are generated in HTML/SVG, to allow dynamic images to display package dependencies etc.

It's quite a new project, but shows potential to becoming a very useful tool. Project is hosted on sourceforge, started by people from the Norwegian tele company Telenor:

XRadar - sourceforge

A Maven plugin would be useful, right now it runs only with Ant. The really cool thing about XRadar is that it can show development over time (different "releases") as in this example. As Maven already has a notion of project versions, it would be very well suited to run something like this.