We are using eclipse and maven for our internal project.
Our project is splitted up into multiple semi-independent projects (modules).
So, using repository and maven eclipse plugin we were able to work. However, there is still one important feature of Eclipse that is not available anymore after we swtiched to maven: sources of different projects got decoupled and you can not search, for instance, for references to some class or method.
This could be only fixed by adding referencing projects' source code from other projects.
So, I decided to write a patch for this.
The point is: during generation of .classpath plugin behaves as usually, with an exception of cases, where groupId is the same as maven.eclipse.localgroupid. For this case there will be an additional classpathentry with reference to project.
Hope, my patch explains more then this text (it is a little bit mixed 
.
Improvement
Open
Major
Ability to add projects of local group to build path
Here patch in plain text:
— plugin.jelly-1.9 2005-10-21 20:13:02.000000000 +0200
+++ plugin.jelly-with-eclipse-project-feature 2005-10-21 20:06:59.000000000 +0200
@@ -48,6 +48,10 @@
<classpathentry kind="var" path="MAVEN_REPO/${relativePath}" />
</j:otherwise>
</j:choose>
+ <j:set var="localGroupId" value="${maven.eclipse.localgroupid}"/>
+ <j:if test='${groupId == localGroupId}'>
+ <classpathentry combineaccessrules="false" kind="src" path="/${artifactId}"/>
+ </j:if>
</define:tag>
</define:taglib>