Currently I'm using Sharepoint 2007 and what im trying to do is this.

I have my main site which has top level information, but then i want to create sub sites for different departments.

Now creating the site collections are ok, and adding users to groups etc.

What I want to be able to do is on the main page, depending on what user and/or what group they're in, have information relating to that departments site appear.

I've looked everywhere for help on this and cant find the answer, Web Parts seem to be hardcoded, as in i have to pick one there that sticks.