Ideas Disclaimer:  these are (random) thoughts of mine that I can’t make into a product or much of anything for one reason or another.  So I present them here for anyone who might use them.

Make a CAPTCHA an instruction for a human to interpret,  like “What’s 2 plus 2?”

Or make it a picture-interpretation.  Ask what is this? and show a picture of a dog.  That does mean that you must be prepared to receive a wide array of possible answers, but its not too hard.  Many a photo are being tagged already.

Or make a multiple-choice test.  Show a question or a picture and ask the user to pick the appropriate response.  You can change the order and wording of questions and responses easily (or rotate pictures) while still making them easy.

Or vary it like this:  tell the user “put ‘answer’ in the 3rd slot below:”  or “put the name of the pictured item in slot 2”.    You then give many slots to place the answer.  The underlying HTML form can have randomized entry names so only the server knows which is supposed to have data returned.

Update: 8-8-09

On July 31, I found a website with this CAPTCHA:

What is the third word in the phrase “laqoc cufuyeg vobipic eqigig cuw”?: