There is a link on the main page that says "View posts since your last visit" which should do the trick. It will show threads with new posts (including brand new threads) since your last logged visit to the board. During the same session, it will mark threads with new posts in yellow (as opposed to dull white/grey if you have already checked that thread during this visit)
If this isn't what you meant, let me know. I'm still looking at a variety of mods and add-ins to make the board more useable, and will likely be asking for member input on such mods as we try them out.