Although it isn't foolproof, what I do is this:
Create a hotmail/excite/etc account for use on the web. Anytime you register on any website, enter an e-mail for anything in a program (like Kazaa or whatever), or whatever it is - use this e-mail. Only check it when a password is being sent to you using it or something.
Your actual e-mail (whether it is hotmail, etc) you keep private and only give it to your close friends and business colleagues.
Most of the spam you'll recieve will go to your web e-mail, because 90% of the time it's the bastard websites you register with who are giving it out / selling it etc. And who cares if the website itself sends you it's trash.. i could care less about new products at xyz.com..
VERY IMPORTANT: If you do get spam to your primary e-mail, DO NOT, I repeat DO NOT EVER, EVER hit the unsubscribe link!!! Do you know what they REALLY put that in for? It's a way to verify your e-mail address! Although they remove your e-mail from their mailing list, they move your e-mail to a "hotlist" which is recently validated, working e-mail addresses - and they sell the lists for even more cash to 20 other mother****'in ***holes on the net so you get twice as much spam. All you do is (A) Get more spam (

Make the ****suckers more money.
Now sometimes, you can't help using your real e-mail (such as when making an online purchase), and if you have a website that you want people to contact you, it is possible for the SPAM scrapers to nail you.
But overall I might get about 5-10 spams a day in my real mailbox, which is annoying still but at least it's manageable. I really feel sorry for you 300 a day'ers.
I do agree though, if there's an equivalent to excorcist-spin-my-head-road-rage towards spam, I have it. The thoughts I have about what I would do to the bastards who manage and execute the lists are far more than morbid, something out of a Cannibal Corpse or Mortician song..
May they pray for their dear souls that I do not ever find one of them.. because it will be a long 1000 hours of straight praying for dear death the end the agony..