This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
This link explains how to define more than one resource bundle within a single module. There's no reason you can't define a common resource bundle in each of your modules along with one unique to that module.
There's one problem, though: You can only define one default resource bundle, and only the default resource bundle can be used for validation and error messages.