I think you'll need to explain, in a little more detail, what you're trying to accomplish before anyone can answer this question for you. What do you mean by many JSPs?
Do you know about the scoped variables that are available to servlet/JSP apps (page, request, session, context)?
Session and application scoped variables are available to all pages in an application, either for a single user during their session, or for everyone using the app.
Also, as Bear mentioned, shared data can be stored in a database.