Upper right, below the banner and header, but above the start of the forum content...
the following buttons are there: Reply, Add Poll, Notify, Mark Unread, Send this Topic, Print.
The NOTIFY button will subscribe you to a topic OR a specific forum category.
Cool. Is there a setting somewhere to automatically subscribe you to threads that you have posted in ?
EDIT: Sweet, just found it. Click Username at top left or click Profile on the Menu bar across the top of the page. This should take you to your Profile Summary page. Here, it gets a bit tricky as there are two different presentations for this page.
One looks like this:
If you get to this page, click the little arrows over on the right that the big red arrow is pointing to. It will then change to this page:
This page will be the one that comes up from now on when you click on your name in the upper left or profile on the menu bar.
From there, click on "Notifications" on the left hand menu bar (the big red arrow is pointing to it).
That will bring you to this page:
Here you can select option to auto subscribe and you can also see the threads that you are subscribed to.