phpBB's captchas (a mod called Better Captcha is even better) and we plan to use it for Pligg, but no work in these areas will be done by us till Monday, if anyone wants to begin it before that - Good!
References:
Check our community site for a workin demo for Better Captchas (phpBB) -
http://dollars5.com/munity/profile.p...er&agreed=true
phpBB better captcha code and link:
http://www.phpbb.com/phpBB/viewtopic.php?t=473222
It uses alpha numeric code and uses font files for captcha displays, instead of all numbers only thing we currently have.