This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
http://tomcat.apache.org/tomcat-6.0-doc/config/context.html Context Attributes - crossContext "Set to true if you want calls within this application to ServletContext.getContext() to successfully return a request dispatcher for other web applications running on this virtual host. Set to false (the default) in security conscious environments, to make getContext() always return null."
alternative would be to use something like JMX, so that you can do "calls" and fetch/put/exchange some data/information between apps.