Well programs like Mailwasher download all your POP3 (and Hotmail) mail for you and categorizes them. If they are on a spam list (modifiable spam server list within Mailwasher), then it can mark them for deletion right away so you don't even have to do anything but hit "process" (ok to delete now). The legit stuff is sorted to the top because those were categorized as good emails (at least not bad).
It's great especially for Yahoo mail since I get 300 emails a day there and my legit mail goes through that account too. Hotmail has cleaned up spam quite a bit on their own.