Go to your profile. In the box on the left, headed Options, there's a link called 'Manage Subscriptions', you'll have a list of your threads and you can unwatch them there.
Thanks for asking Grayorm.
I didn't know either and sometimes the thought of getting an email every time there is a new post can out you off chipping in.
I think we are confused
'view your posts' will list all the threads that you have had any input into. I do not think it is possible to trim this list.
'unsubscribe' will only appear if you have 'subscribed'.