Have you ever thought about making tab that would show all new threads from any of the different forums? Kinda like the resent post on the upper right side of the site.
I'm not sure if this is what you are asking about but after you have signed in under your name in the top right corner there is a link that says "show all unread posts since last visit" written in red.
As ribo451 stated, if you go to the top of the page, right under where it says "Hello Rich Z", there is a red link that says "Show unread posts since last visit"...is this what you're looking for? It's different than the "Recent Posts" section on the right side of the page...