Is there a list of all disclosed security breaches somewhere?
There is even an RSS feed. It doesn't cover every breach but certainly significant verified ones - details in the site FAQ. There is even such a thing as faked breaches!
I also alias email addresses for every service that allows a + sign in the email field, so now I have no way to notice quickly if the email was included in a leak. But I do have a way to know which service got breached or sold info if I start getting additional emails to any particular alias.