Hostmonster (a Bluehost brand) have been the worst, since they were so blatant about it. I'd only had legitimate correspondence to that address, until the week I cancelled my account, and since then the spam has been relentless. So as part of my account cancellation, they clearly sold my email address on.

The most amusing was the UK Parliament petitions site, since you would have thought they were a bit more careful with the email addresses given to them.

But the strangest is the persistent use of specific email addresses that I've never used anywhere - about half a dozen common forenames, and one forename-plus-three-numbers. I've no idea where they originally came from - perhaps someone padding out their email lists for sale with semi-randomly generated ones? - but that set of addresses has been used and reused for over a decade. At least it makes it easy for me to train spam filters, since even novel emails are easy for the filters to spot when multiple copies arrive together.