This is not a particularly elegant answer, but it may serve your purposes.
You can use the maven-dependency-plugin to output the classpath to a file. The build-classpath is the relevant goal. the configuration below will output Maven's classpath to [project directory]/target/.mavenClasspath
You could write a small script or ant task to read the .mavenClasspath file contents and append the entries to the Eclipse .classpath. If you make the script a bit smarter and remove previous entries, then set it up as an external builder, you have a nearly integrated solution.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>output-classpath</id>
<phase>package</phase>
<goals>
<goal>build-classpath</goal>
</goals>
<configuration>
<outputFile>${project.build.directory}.mavenClasspath</outputFile>
</configuration>
</execution>
</executions>
</plugin>