Using Eclipse and Maven is a useful pointer to working with the two. However, in Eclipse 3.1, the place to configure the build variables has changed slightly: you now need to go to Window -> Preferences -> Java -> Build Path -> Classpath in order to add the MAVEN_REPO variable (which should point to something like ~/.maven/repository).
If you have a multiproject setup (using Maven 1.0.2), to get running you also need to do:
maven multiproject:goal -Dgoal=eclipse
maven multiproject