I'd like to be able to track forum threads by clicking on a checkbox on the page. Label it something like "Track this thread". Also, automatically turn tracking on if I post in a thread.
If I decide later that I don't want to track the thread anymore, I can just un-check the checkbox for tracking.
This would be invaluable if I'm in an interesting discussion that gets held up a couple days because someone got a bit too busy. Once they came back and posted, I'd immediately know it and things could continue where they left off. As it is now, I have to manually check all forums and see if any of my topics have new posts.
When new posts appear in a tracked thread, I get a notification that there are new posts (maybe an icon to the left of the message icon?). If I click on it, it goes to a page with links to all of the threads that have new posts.