Creating a multiple publication portal

Hi All

I am currently working on a project where we are creating a portal to
various publications. Users who are registered with the site can
subscribe
to various publications.

Each publication has content which may vary greatly in content
structure.
Each publication will function as a subdomain →
publication1.sitename.comand
publication2.sitename.com will be to seperate publications with seperate
look and feel.
There will be some generic portal functionality (glorified breadcrumb)
to
get back to the portal section aswell as some publication specific
functionality.

My question:
What would be the best way of architecting a portal such as this in the
context of Rails (2).
One way, would be to have a seperate app with shared sessions. Another
way
would be to extract publication specific code to a set of plugins or
mixins.

Any quidance would be appreciated.

Regards
Ivor