Go to "User CP".
On the left hand column, under "Subscribed Threads", click on "List Subscriptions".
In the center, click on "View All Subscribed Threads". You will see all your subscribed threads.
Check the box next to threads you want to unsubscribe to, and then do so via the pull down menu.
Hope this helps!
Already we are boldly launched upon the deep; but soon we shall be lost in its unshored, harbourless immensities. - - H. Melville, 1851.