Unsubscribing from email messages that you never asked for is a tricky business. In many cases clicking on the included unsubscribe link in the email only acts to verify to the spammer that your address is valid.
Here are some ways to remove (or at least attempt to remove) your address from a spammers list.
Unsubscribing from Spam
Before you automatically reach for the "Mark as Spam" button provided by your email client, pause for just a moment and try to recall if the email was at one time requested.