Junkanoo

Junkaoo is easy to configure, and it works with multiple inboxes. It's configurable, letting you set how aggressively it should check for spam. In addition, you can add white lists and entire domains that won't be marked as spam, for fewer false positives. The software is also a kind of mini e-mail client, so you can read and respond to mail and create new mail as well.

--Preston Gralla