reCaptcha
This plugin is compatible with the Movable Type 4 Captcha API, which uses reCaptcha as its CAPTCHA image provider.
The plugin users are required to register their blogs to recaptcha.net and get public/private key pair, in order to use this plugin.
Step-by-step guide can be found in the README file in this plugin.

mashby.pip.verisignlabs.com
April 8, 2008 3:03 PM | Reply
This plugin doesn't work on a default 4.1 Personal install. The instructions regarding the JavaScript template simply don't apply and I assume that's the reason it doesn't work.
Attempting to go back to version 0.1 since I did get that version to work.
Fumiaki Yoshimatsu
April 8, 2008 5:31 PM | Reply
The plugin works fine for me on my default 4.1 Personal install. I am curious which line in the README does not apply. Would you elaborate it a little more, please?
Ryan Brodkin
April 14, 2008 10:37 PM | Reply
I used it on a default 4.1 personal install successfully as well, but I wasn't thrilled that it doesn't install cleanly as just a plugin.
mikeheu
June 30, 2008 3:23 PM | Reply
I've had it installed and it was working fine for anonymous comments. While enabled, though, the registration to the blog does not work. If I turn off reCaptcha, it works fine. Anyone have a solution for this?
Jon C
July 23, 2008 5:15 PM | Reply
registration is definitely broken - captcha does not show up.
Fumiaki Yoshimatsu
July 23, 2008 6:47 PM | Reply
@mikeheu @Jon C Sorry about that. It was a bug and I think I was able to fix it in the version 0.21. It would be great if you could give the new code a try. Thanks for the report!
Stephen Walsh
February 14, 2009 10:31 PM | Reply
Still no go on the registration. It seems to be in an infinite loop without actually verifying the text as correct even though it is entered correctly.
tmtauchi
April 21, 2009 10:53 PM | Reply
I am having the same problem as the commenter before me. I am using MT 4.24 and followed the instructions you outlined. However, when I test the Recaptcha, every single time I get the same error message: "Text entered was wrong. Try again." I can't seem to find any info on any of the discussion forums on how to fix this...