As someone with a web presence since mid 1995, I've had my fair share of spam, and I don't like it (does anyone ?). Originally I used a Win32 pop proxy based on the excellent SpamAssasin called SAProxy. This was expensive, but worked well.
Unfortunatley in 2004 the company, Stata Labs was aquired by Yahoo mainly for it's mail client. Yahoo has since announced there will be no more development of SAProxy.
Luckily this encouraged one of the original development team to release a new version called SpamFu . It's mostly open source and does everything SAProxy used to d, and more !
Neither SAProxy nor SpamFu are one click installations, but they are quite easy, and very effective. With up to date rulesets and blacklists I recon my setup catches 99% of SPAM with almost no HAM being caught.
