Meet Steve Bass. Steve blogs at pcworld.com. Watch Steve blog. Blog, Steve, blog. Steve just blogged a bunch of spam filtering resources. Unfortunately, his list is heavy on the challenge/response FUSSP meme. Ooops!
For the record, Choicemail's "unknown-sender registration" and the "bounce" features of MailSnoop and MailWasher are really terrible ideas. (Don't forget that the "sender" of spam is almost always forged.)
I do wish consumer-focused journalists like Steve wouldn't promote these features -- he'll get his readers blacklisted, causing their email not to go through.
For more background, see: