We had it working a while back, before we switched to using a single VM. Tomcat 5.5 was running in one VM and JBoss with EJB3 was running in another. You need to add the client jars to your web applications. It is a little tricky finding the right jars. Also you shouldn't take the jars from the JBOSS_HOME/client directory. Take a look at the EJB3 Installation guide. Towards the end there is a list of directories which contain the correct jars to use.
If you post more details on what you have tried and where you failed you might get more detailed responces, but in general it does work.