you have a couple options.
1) you can place them in the "lib" directory under JBOSS_HOME/server/default. any libraries placed here will be available to all deployed apps. there is no way to update libraries here w/o a server restart. jdbc drivers are good to place here.
2) you can place them directly in the deploy directory.
3) you can package them inside your ear/war/sar
seperate library versions can be accomplished using loader-repositories. however, you may have problems if app1 needs to talk to app2 and they use different library versions.