The solution to most spam these days is simple: get a Gmail account.
For those who don't have the option, or want that bit of extra protection, it's time to enable a spam filter.
Able to monitor Outlook, Outlook Express or Thunderbird, BullGuard's latest iteration of its aptly named Spamfilter program analyses your existing good and bad email and starts building rules from there. It also draws on BullGuard's spam database to knock out known spam emails, and maintains a whitelist and blacklist of email addresses, so you can either stop email from friends being blocked or damn that prince from Nigeria permanently.
Most interestingly it comes with free 24/7 support -- meaning at the very least that it's worth a bash. Sadly it's only built for the 32-bit versions of Windows Vista, XP and 2000, but if that includes you (and that's the vast majority), then you can download the 14MB program with abandon from here.