What you need is a crawler page or set of crawler pages.
One page that lists the forums just as plain links, i.e. forums.htm
The links on this page will link to other pages called f1.htm, f2.htm, etc. One for each forum.
Each f??.htm page will then have a list of links on them to the actual topics on the site.
You can then submit the one forums.htm page to the search engines and let it rip.
Most search engines are experimenting with dynamically generated pages or they only spider a few pages. They also have a tendency to get lost inside a forum with the many, many links.
It's easier to setup a crawler page and use the robots meta tag, to tell the crawler to follow the links on the crawler pages but not to index them. And then on the forums, add a robots tag to the forum header that says (index, no follow). This should mean your content is indexed, the crawler pages are not and the spider doesn't hammer your site following all the reply and edit links on all the forum pages.
This is a theory at the moment but one I'll be trying shortly. I want all my pages indexed internally and externally and this seems the easiest way around it. However, I can't write Perl so I'm going to use PHP to generate the pages from the UBB files.
If I get this working I'll share it here.
