Go to the "User CP" link on the upper blue bar (left side of page) and click the tab.
When you get to the next page scroll down to "Subscribed Threads" on the left column and click it where is reads "List Subscriptions".
Any threads you are subscribed to will be listed on that page.
Check off the box located to the right of each thread, then open the "selected Threads" tab on the lower right corner and click on the "Delete Subscription" box and hit the "Go" button.
"You wouldn't worry so much about what others think of you if you realized how seldom they do."