NuCaptcha offers video-based CAPTCHA prompts, easier for humans
Like spam filters, Captcha is one of the necessary evils of the Internet. Google's Captcha is consistently irritating for me. I routinely fail it at least once, sometimes twice in a row, and I'm not a robot (to the best of my knowledge). Google bought reCAPTCHA a while back, and it's nicer (and helps a good cause), but they still seem to be using their older, super-irritating Captcha in many places.
The problem with Captcha is that it's irritating to users, and it can also be quite easy to break. Many programs and spambots contain built-in Captcha-defeating mechanisms that use sophisticated OCR to figure out what the image says, and they're often quite good. So, everyone loses; the users get an irritating interface, and the sites still get automated "visitors." And the harder the sites fight the bots, the more irritating it gets for the users.
NuCaptcha offers a completely different take on the issue: use video! You get a nice, customizable Flash video window with a bunch of text scrolling from right to left. The letters wiggle a little bit but are quite legible otherwise. You only need the last three letters of the string, which show up in red, and are (apparently) random.
It is much harder to apply OCR to video, so NuCaptcha can afford to be very legible, at least for now. I think it's a brilliant solution, and I can't wait to see it on more websites.