Good Form Security - no CAPTCHA

Question

Is there a good method of form security that does not involve CAPTCHA? CAPTCHA is so annoying, but I need security because I am getting form spam. My form is

Answer 1

If cutting down spam is the immediate need, putting the form in an iframe has been effective for me.

Set the frame's height and width a little bigger than your form's width and height. Use CSS to make the frame border 0 so users won't notice they're looking at the form within frame.