I'm not an anti-spam warrior like many IT people are. There are a number of relatively easy steps that anyone can take to reduce the amount of spam and I'm not even referring to sometimes-intrusive spamblocking software:

Do not insert your email address in to any form, ever. I have a spambox that I use to insert in to fields that require an email address. You can get free email services from Yahoo and Hotmail for free that you can use. You can use that address for web sites that require sending an email to you (some quizzes work that way), comments sections that require an email address (or you can just put in a fake one), and services that get sent to your email box (for instance, my credit card payment reminders go to my spambox, though this requires knowing about when payments are due).

Do not use your email address on Usenet or message boards. You can try tricks like name-at-domain-dot-com, but more sophisticated email harvesting programs will decipher it. I personally use my spambox for what few message boards I'm apart of. I check my spambox once every few days. I look for anything worthwhile and then "delete all."

Yahoo (and possibly hotmail) have pretty good spam filters. There are a few false positives, but it does a remarkable job getting rid of a lot of spam. That said, Yahoo and Hotmail are hotbeds for spammers since they often have public registries. For all of my problems with Bigfoot, I get surprisingly few spam through them.

If someone sends you an unsolicited email and at the bottom it says "remove", be wary before actually doing that. As often as not, those are used to verify email address. When they get that, they know you've gotten the email and they can get more money for selling "verified" email addresses.

Having said all that, the recent "crackdown" of spammers does not seem to be working. My Yahoo email box holds on to suspected junk-mail for about a week before discarding it. In the average week, I used to get about 60 items, but now I get 145 or so.

Speaking of spam, InfoWorld has an interesting (if short) article on Jon Postel, one of the founders of email protocols. Apparently from the start he was concerned about the proliferation of junk mail, but his warnings went unheeded. Realistically, though, I'm not sure what all can actually be done about it that isn't already being done. What's easy for you and me (one of email's selling points) is easy for scummy businesses.