MailWasher gets my vote. Run it before collecting your email and it will go through and mark everything it thinks is spam. Check the selection and then hit a button and its gone.
It can work of various spam lists as well, eg spamhaus.org, so it picks up known spamming sources which is where most of the junk comes from.
Its free, simple to use, works on multiple accounts, and you get to keep your current email program too.
http://www.mailwasher.net/