I think Alfresco can do this...

[edcincy]

Ok, here is the scenario.  Supposed there are several local businesses that need a document repository for some of their documents.  Each of these businesses is a separate entity and should have no access to documents of the other businesses.

Is it possible to install Alfresco on a server, create a site using WCM, create groups (each business would be a group) and users within those groups (the employees of those businesses) and allow them all access to the same Aldfresco instance using permissions and privileges for each business and employee?

Down the line, new businesses would be added (by me) and groups and permissions created and set.

Can Alfresco do this as a stand-alone product, or would it be used as a "back end" to a Java/JSP site which then retrieves and shows information for each business as it was requested?

Thanks in advance for your help.  I'm still trying to make sense of what all Alfresco can do!

[mrogers]

Answer: all of the above.

You may also be interested in the feature called "multi-tenancy" which will allow multiple "tennants" in your case one for each business.

[edcincy]

The more I learn about this product, the more it amazes me.

If I was to use the Community Edition for this purpose, would it be possible to "brand" the installed Alfresco product or would it be better to create a branded front end to the repository?

Also, any opinions on the book "Alfresco Developer Guide"?  Would this book help in the creation of such a site?

[mrogers]

Yes you can add your own branding.   

Whether to put another UI on top of Alfresco is up to you.  
I'd suggest you get used to using what's there allready and once you understand it to make a decision whether a few tweaks here and there will be sufficient or whether you need to start with a more significant piece of work.