I've re-added a small link at the bottom of the forum in the Forum Information that says "View Active Threads". We used to have this but ran into problems, but I think I have this resolved. Give it a whirl and let me know if you have problems.
Basically by default it shows any posts in the forums that have been updated in the last 24 hours. You can also set it to view updated threads the last 3, 5 or 7 days. Some people find it useful. I find it a little overwhelming, but that's just me!