New member introduction

Among other things I run a nonprofit which publishes educational material
and news for the independent inventor community.  I am looking for
recommendations of how to implement a method where people without html
experience can update web pages.  This cannot take the form of a weblog, in
that they need to be able to create content or to edit content.  Think of it
more as a virtual book which is continually updated by nonprogrammers.

I have discovered that there is a great deal of pen source software and now
the problem is figuring out which will do what I need.

I need to migrate the current html content to the new system.

I would also like to have access control based on user name + password where
each subscriber to the site has different levels of access.

I would like a method of collecting monthly or annual fees which would in
part determine the users level of accessibility.  Those contributing time to
the site would have access without paying fees and some content such as the
children's section would have free access.  This has become necessary
because the majority of people who use our resources do not contribute.

At this time the web site has in excess of 500 web pages and management of
the site needs to be spread among more then one person.  Traffic runs
between 50,000 and 100,000 page views a month.

Suggestions please.

Ronald J. Riley
www.InventorEd.org