wpdebuglog

This is a highly powerful contact form 7 anti-spam add-on. It is introducing a new hidden field and check that one value is correct or not.
<h4>Features of Contact Form 7 Honeypot Plus</h4>
<ul>
<li>No configuration is needed</li>
<li>Better anti-spam functionality</li>
<li>No need any ugly captcha.</li>
</ul>

Contact Form 7 Honeypot Plus

Nice plugin

Contact Form 7 Honeypot Plus - Adds honeypot plus anti-spam functionality to Contact Form 7 forms.

WP-Biz (Ryan)

The “honeypot” technique for SPAM protection is invisible to humans, and tricks robots into filling out an invisible form field. Then, if that invisible field has been filled, the form cannot be submitted. Easy, non-instrusive SPAM protection.
No settings to set, this honeypot is added to all Formidable forms on your site, unless the user is logged in. When SPAM is suspected, the form will not be submitted and the visitor will be alerted to this fact.
Tested to work with both Formidable (free) and <a href="http://www.wpbiz.co/go/forms" rel="nofollow ugc">Formidable Pro</a> (best bet for awesome form power!)
A note to Formidable Pro users: You paid to receive extra features in the Formidable plugin. Me too, it’s well worth it. This Honeypot plugin, and Ryan (the developer) are not connected to Formidable in any way. Since this adds another very helpful feature to Formidable, I ask you to send a <a href="http://wpbiz.co/donate/" rel="nofollow ugc">donation at WPbiz.co</a> to say thanks and encourage future developemnt.

Formidable Honeypot

Add SPAM protection to your Formidable forms without annoying your visitors with Captchas, math, or other fields.

Contact Form 7 Honeypot Plus vs Formidable Honeypot