I need to build a site that uses multiple themes. I'm looking for suggestions on the best way to do it. I'm sure it's not to hard I just don't want to spend tons of time doing it an inefficient or impossible way.

Ok, Heres what I'm doing. I have a domain (domain.com)for a site that has products which each have their own section of the site (domain.com/productx, domain.com/productz, etc.).

The site will use a news module for updates, with different news showing up in different sections and the front page based on topic. Some news will need to show up on all product pages.

Now so far this is basic. The trick is each product section needs to have a different theme and the root domain has to have it's own as well. Any ideas on how best to do this?

Thanks.
-Ray