Tonye, what email program are you using and how do you have your filters set? Mail is apparently quite good at filtering spam - Entourage works fine for me, but I don't get much junk. I have filters set so that anything that isn't addressed to me personally ends up in a "Junk" folder, which I check occasionally.
I am absolutely scrupulous about preventing it in the first place - my primary email address is NEVER used to sign up for anything (and I usually don't sign up for anything either) and I also don't use my primary addy online - on web sites or message boards. I also never register anything I don't have to - including software.
The best way I know of getting rid of spam and starting over - get a new email address. Your ISP should be willing to do this for you. Some of them even allow you to do it online. Then just send out an email to everyone in your address book or whoever you want to have your new address and voila - at least for a while. And if you're extremely careful with that new address, then you may find you don't start getting junk again. Some ISP's are much better than others too - ATTBI seems pretty good - I'd imagine having an AOL or Hotmail address would be a spam-magnet of the first order, simply because sending stuff to those domains is likely to be more profitable for the spammers (more customers).
Also, don't ever, ever, ever reply to those "remove me from your email list" options that so many spammers use. They won't remove you - they'll just know they have a "live one" and add you to every mailing list in creation. Those lists are sold and resold - replying once or twice could be all it takes to get you on lots of lists! Bouncing spam almost NEVER works because they aren't using real return email addresses. They're all spoofed.
You can also report spam through spamcop.net - at least then your complaints have a reasonable chance of landing on the actual sending ISP's desk, though of course, some of them couldn't care less, as they exist almost solely to serve spammers. However, if it is a real ISP, serving the general public rather than the spamming industry, like ATTBI or AOL etc., then they will care, and take action against the offender(s). Spamming is against the terms of service rules for most reputable ISP's.
Hope that helps a bit - there are other solutions - some here have bits of software that they find helpful, but I've never needed to go that route, since becoming zealously careful about my email addy and what I do with it.