I don't think there is much on this. Normally, you wouldn't really need to bother too much with the default vanilla Management Packs, they are pretty much required to make a base installation work. Their name and description should give you an idea of their
purpose.
The ones of more interest are some of the unsealed ones such as "Service Manager Incident Management Configuration Library". This can end up storing a lot of your Incident views and other Incident class configuration by default.
It is a very good idea to make daily backups of all of your unsealed Management Packs just in case.
Steve Beaumont has a solution for this on the Technet Gallery here:
http://gallery.technet.microsoft.com/Service-Manager-2010-9fd2ea90
Or, I have a custom assembly that does this somewhere.
There are lots of other Management Packs available for download from here, too, which should hopefully answer your "portal" question.
Whenever possible, when creating something new, you should create a new MP or choose one of your new existing ones to store the item in. For example, create a new MP to store all of your list items in.
As time goes on, what you would really want to document is what all of your own Management Packs do and store, etc as well as any custom solution ones that you happen to create or download and import. These will be the ones that people will need to know
about.
Hope this helps!
Rob Ford scsmnz.net