I get these all the time. I have a main (ISP) email that I use sparingly and only for important stuff, like my WoW accounts, and a couple of free junk emails that I use for forum sign ups and such like. I always get these type of emails in my junk accounts so it's obvious straight off the bat that it's junk.

My ISP also allows me to set-up different email addresses for the same account and if I'm shopping I can just use shopname@myaccount.com which works without me changing or setting up anything, then I can see if any sites are passing my email address on.