Following installation of plugins from update sites:
1. Mylyn
http://download.eclipse.org/tools/mylyn/update/e3.4
2. Subclipse
http://subclipse.tigris.org/update_1.6.x
3. Maven Integration for Eclipse AJDT plugin (required for 4.)
http://download.eclipse.org/tools/ajdt/35/dev/update
4. M2Eclipse
http://m2eclipse.sonatype.org/update/

...and setting up a Maven Webapp project:

File->
New->
Project ->
Other->
Maven->
Maven project ->
Wait for Nexus Indexer Update ->
Select maven-archetype-webapp -> Select Next ->
Accept the defaults. Click Next ->
Enter the GroupId and ArtiactId. Click Finish ->
Project is set up but returns error:

Message:
An internal error occurred during: "Creating maven-archetype-webapp".

Stack Trace:
java.lang.AbstractMethodError
at org.maven.ide.eclipse.internal.project.DefaultLifecycleMapping.configure(DefaultLifecycleMapping.java:64)
at org.maven.ide.eclipse.internal.project.ProjectConfigurationManager.updateProjectConfiguration(ProjectConfigurationManager.java:347)
at org.maven.ide.eclipse.internal.project.ProjectConfigurationManager.configureNewMavenProject(ProjectConfigurationManager.java:269)
at org.maven.ide.eclipse.internal.project.ProjectConfigurationManager.importProjects(ProjectConfigurationManager.java:165)
at org.maven.ide.eclipse.internal.project.ProjectConfigurationManager.createArchetypeProject(ProjectConfigurationManager.java:533)
at org.maven.ide.eclipse.wizards.MavenProjectWizard$5.runInWorkspace(MavenProjectWizard.java:280)
at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

Session Data:
eclipse.buildId=M20090917-0800
java.version=1.6.0_16
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=linux, ARCH=x86, WS=gtk, NL=en_US
Command-line arguments: -os linux -ws gtk -arch x86 -clean

Everything else is fine. (ie project builds etc.)

Ben