I filed a patent application for a new CAPTCHA technology. The details do not belong here (much, much too long) but if you are interested you can see them in my Warrior Forum blog The Proof-of-Work CAPTCHA.
Basically, what I am doing is combining a distorted-character captcha with something called a "Proof of Work" which is way to force the user's browser to carry out a complex computation of my choice, similar to HashCash and Bitcoin.
For an ordinary user this is no great burden, all they will see is that their computers will have a slightly higher processor load than normal. For the spammers, though, it will be a disaster.
The key is that, in general, automated spamming tools do not use a full browser, so they will not be able to produce the proof-of-work, and in any event the proof-of-work calculation will increase the amount of computation required well beyond anything reasonable (from the spammer's point of view).
I wonder if I can ask the warriors in this forum to suggest the best way to market this technology, and/or any ideas, suggestions, critiques (flames!) etc.
Joe (aka mekDroid)