Two years ago, I published a Maven archetype for Hadoop that turned out to be quite popular, judging from the comments I received and the access logs on my server. Today I've updated it to use the latest version of Hadoop and to build on Maven 3 without warnings.
Like previously, creating a new Hadoop project works like this:
mvn archetype:generate -DarchetypeCatalog=http://dev.mafr.de/repos/maven2/
Select the Hadoop archetype from the menu, answer a few questions and you're done.
You'll notice that there's a second archetype jar-project-basic which is an improved version of Maven's quickstart archetype. It comes with extended unit testing support (JUnit, Hamcrest, Mockito) and also includes dependencies to Google Guava and slf4j that I use frequently.