I think the HARDeployer and infrastructure is meant to be working out-the-box.

I found both hibernate2 (from 4.0.2RC1) and hibernate3 (from 4.0.2-final) both have an external dependancy on org.apache.commons.collections to fix this problem I copied:

$ cp commons-collections-2.1.1.jar $JBOSS_HOME/server/default/deploy/jboss-hibernate.deployer/

18:30:09,797 INFO [Server] JBoss (MX MicroKernel) [4.0.2 (build: CVSTag=JBoss_4_0_2 date=200505022023)] Started in 1m:1s:692ms
18:30:55,574 INFO [Environment] Hibernate 3.0.2
18:30:55,595 INFO [Environment] loaded properties from resource hibernate.properties:

18:30:55,597 INFO [Environment] using CGLIB reflection optimizer
18:30:55,598 INFO [Environment] using JDK 1.4 java.sql.Timestamp handling
18:30:56,026 INFO [Hibernate] Using JDBC batch size : null
18:30:56,064 INFO [Configuration] Searching for mapping documents in jar: DLMC.har
18:30:56,065 INFO [Configuration] Found mapping documents in jar: uk/co/dlmc/Customer.hbm.xml
18:30:58,491 WARN [ServiceController] Problem starting service jboss.har:service=Hibernate
java.lang.NoClassDefFoundError: org/apache/commons/collections/SequencedHashMap
at org.hibernate.mapping.Table.<init>(Table.java:33)
at org.hibernate.cfg.Mappings.addTable(Mappings.java:116)
at org.hibernate.cfg.HbmBinder.bindRootPersistentClassCommonValues(HbmBinder.java:250)
at org.hibernate.cfg.HbmBinder.bindRootClass(HbmBinder.java:235)
at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:151)
at org.hibernate.cfg.Configuration.add(Configuration.java:360)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:397)