Ok, this site is falling victim to what is called split PR, it is when your site has a / and a index.php. Like this one, if you go to / you have a high PR, if you goto /index.php you have a low PR. You need to edit your links that point to index.php or index.php? to point to /. This will better your PR and will help with your site ranks. I did this on my forum and my site ranks and PR both went up.
I hope that was the kind of feedback that you are looking for. I was blunt about it.
Someone brought this up in the past (may have been you).
I am not sure how to fix that. I think all vB do that. But, there is another link back to the home page which is hard coded with the full URL so there is still a link on every page going back to the hompage...
I've found that most (if not all) forums do this. Thats' why most (not all) forums don't show up on Google searches.
We have several nice search engine rankings for this forum. vB3 also includes an archive which is spiderable by Google (Google does also list any of the regular PHP pages but not near all of them (Google is getting better at this).
Anyway, the index.php? link is something I may try and get modified but may not get to it right away. I'll do some more research on that. ATLien, I'll let you know if you can help out.