I have used many captcha's in Joomla (you know - when you have to type in words or do a little math before you can send in a form).
They are often used for a contact form in Joomla. But the bad side is, if you want a Joomla contact form with a captcha, you often have to use a 3rd party contact extension. While I like the Joomla contacts the best and don't want to get rid of that.
I found a great way to get the best captcha around into the Joomla contact page:
Re-captcha is 2 parts. One side is an extension other part is 3rd party account.
The extension:
http://www.joomlaez.com/joomla-plugins/ ... ution.html
The recaptcha:
http://recaptcha.net/
Make an account there and you will receive 2 codes that you have to use in the extension.
To have it in a normal Joomla contact page ( I really don't like most 3rd party contact thingies and try to maintain to defaults)
Easiest way is to use a template overwrite (ie a copy of the contact php but in a way that joomla upgrades still go ok)
to make the contact page template overwrite. Copy /com_contact/views/contact/tmpl/default_form.php and put the copy in: /templates/your_template_in_use/html/com_contact/contact/default_form.php
in the file, find:
[code=php:3sdj6y0i]<span class="syntaxhtml"><button