I was seriously considering creating a new account and just abandoning my current one.
As a last ditch effort, I decided to unsubscribe or opt-out whenever possible. I assumed I would probably end up getting even more spam.
Amazingly, it worked. It took a couple weeks of unsubscribing to actually see some results, but now I am averaging a couple of spam a day. Not too shabby.
I also learned that you need to opt-out more than your own email address. Yahoo! regularly delivers spam which is sent to email addresses similar to yours. Too smart for its own good.
Another tip: Create a filter that moves all emails not directly addressed to you to the trash.