m2eclipse is a Plug-in for the Eclipse IDE that defines Eclipse Project structures by analyzing Maven Project models.
From the m2eclipse Project Home Page:
m2eclipse provides comprehensive Maven integration for Eclipse. You can use m2eclipse to manage both simple and multi-module Maven projects, execute Maven builds via the Eclipse interface, and interact with Maven repositories. m2eclipse makes development easier by integrating data from a project’s Object Model with Eclipse IDE features. With m2eclipse, you can use Maven within Eclipse in a natural and intuitive interface.
m2eclipse is a renaming of Sonatype's m2eclipse when it was transferred from Codehaus to the Eclipse Foundation in the Indigo (3.7). Sonatype is still involved in building m2eclipse, and the latest bleeding-edge releases are available on their website.