We are currently implementing a consistent look and feel across all of our web applications within our new administrative portal system.  What I have done is to create jsp pages that define the header and footer, which are included into each page within the portal.  The footer is mostly static, but the header changes slightly depending on which portal the user is in (students, faculty, staff, alumni, etc) as do the main menu options along the top of the screen.  This is all controlled by the system administrator (me) and only the body of the page is left to the application programming teams.  I also have a convenience JSP that the application programmers can include in their pages to populate a dynamic menu along the left side of their web application, to which they pass  parameters relating to the menu items and the links associated with them. 
Each of our portals is within its own context, but the administrative jsp pages (header, footer, menu generator) are in a separate administrative context.  The flexibility is great and those includes don't seem to slow anything down (even though they have to be run-time includes), but it has NOT been tested under heavy load yet.  Let me know if you have any further questions.
               Allen Akers
               Programmer Analyst
               Strategic Web and Voice Development

>>> David_Aiken@bmc.com 12/07/00 09:01AM >>>
hi all..

We're creating several web applications which must share a common look/feel.
We have thought of combining them into a single webapp - this will work, but
requires a convoluted install/upgrade/uninstall strategy. I suspect that
objects kept in the session context will persist across apps on the same
server, and the CLASSPATH could hold any required classes for tags et al,
but i'm not sure if  tag library declarations or includes of JSP pages/CSS
style sheets across app boundaries would work. Does anyone have a useful
strategy to solve this problem?

david aiken