App Developers, how do YOU stop bots?

I would suppose this is mainly intended as a question for Nik and my man Olaf  :P

What i am curious of is, what methods are you using to stop spam bots from registering and performing other $_POST?> actions on your applications or scripts; aka commenting, posting thread, etc whatever it may be.

Obviously it starts with image verification or CAPTCHA as the first line of defense, and this works great usually! But i have read some articles that suggest some spam bots are getting advanced enough to get past these types of attempts to stop spam, so it's only effective for a short time.

I am afraid that with phpHaze (at the moment it is utterly depended on the image verification to stop spam registrations) will eventually break down to spam bots and image verification will no longer be enough.. So what other methods do you use? I've seen talk about asking the user to do some math, but I would rather require as little user input as possible, and depending on the script itself to stop all kinds of spam...... so what do you think?

1) Load the form with AJAX
2) Use non-common field names for the post variables (check the registration page here)

check this tutorial:

http://www.finalwebsites.com/tutorials/php_ajax_contact_form.php

thanks for the idea with field names, Nik -- i will surely do that first! i will have to look into this ajax thing, thanks for the tutorial Olaf!