how to get a nice jar out of my modules

[Sa...@swisscom.com]

Ive got a project "base" set up with some modules "exception", "logging"
etc, its perfectly fine for me that each module produces a jar with its
version (eg. exception-1.0.jar) but is there an easy way to create a
base-1.0.jar which contains all classfiles and resources in my modules. 
I tried the assembly plugin, i.e. I created an assembly xml file and
configured the assembly plugin in base's pom.xml to read it, but it
tries to find the assembly xml in the first module's source path of my
project.