Whenever I expect something to send me more email than I want, but I also might need to respond to one email from them (account confirmations and the like) I give them a gmail address that exists solely as a spam reactor.

It’s actually set to forward to my hotmail (so that I can use it for things that I do want to receive mail from, but don’t want to give my main email to) but there’s a set of filter rules for what gets forwarded and what doesn’t. Makes use of how you can send mail to myusername+whatever@gmail.com and it’ll find its way myusername@gmail.com – then you can use the +whatever in a filter rule.

Either give out emails in the form myusername+theirname@gmail, so you know who gave your address to spammers and can block accordingly, or (as I do) have a standard “don’t forward it” filter for the ones where you know there’s going to be spam.

Unfortunately my hotmail seems to still be on a few lists for viagra-spam and camwhore-spam, but compared to the crap hitting the spam box on that gmail it’s pretty tame.