It's the least I can do!! I've been lurking for so long, I almost feel like an information thief :)
Before I continue, I would like to say that this is a mixture of methodology I came across, like Fusebox, Freenergy and such content and application management. I simply blended what I liked together and reworked some parts to accommodate my needs.
I'll start with a really basic example just to give you an idea (Don't be shy, I'm sure there is flaws with that setup so feel free to point the problems out).
Ok so you got your domain hosted with PHP, MySQL and mod_rewrite available. Now your company sells blue and red widgets, so your available pages could look like this:
So basically, I'm saying that you have a bunch of pages available in your root, blue-widgets and red-widgets directories but they don't physically exist as is. Let me explain.
It's where mod_rewrite comes into play. I'll assume you can setup rewrite rules and such (if not, you can find all you need using the search at the top of this page). Every request gets rewritten to a script I decided to call (no particular reason) fetch-page-data.php (for example: www.mycompany.com/blue-widgets/features.html translate to a request for www.mycompany.com/fetch-page-data.php?fp=/blue-widgets/features.html).
Our next step is to consider what our fetch-page-data.php will do. That's where I think all this start to make some sense (hopefully :)). For our example, this script's first task is to query our database using the variable fp. Let's pause for a second and talk about our database schema.
A really stripped down version again, but let's say we simply have a page table with fields like title, meta-keywords, layout-file, header-file, menu-file, content-file (you get the idea) just to name a few and most importantly file-path. (Which is used to get a match from our fetch-page-data.php script)
Now that our script located the data for a specific page, it simply includes the specific layout file using the layout-file from the record set. (Then again you could take care of actions prior to this step, like saving some customer info or updating session variables and such). The layout file then include whatever it needs like meta keywords, menus and content according to specific look and feel.
If no match is found in the database, simply send a custom 404 and you're set.
This is getting quite long, but I just wanted to specify that you'll have to set up some sort of include folder where all your layout, menus and content files will be.
Hope this is useful.