On threads with activity that you have not seen, you get the little blue "New" deal next to the subject. If you click on that, it goes away. Essentially a "mark as read" feature. This is pretty useful. A lot of times I have threads that I have posted in but then cease caring about because it drags on forever, so I end up going through my list of threads and entering each one just to leave immediately so it can be marked as read.
Hopefully I'm not the only one who didn't know about this.
I'm used to clicking on the new icon on other forums to bring me to the most recent post, so I found out a very long time ago that on this forum it just marks the topic read. It's unfortunate there is no way to conveniently go to the first new post though.