WP Captcha-Free is a lightweight plugin that blocks automated comment spam without using captcha (image verfication).
I use this on every website I build, professional or personal. Fantastic and really cuts down on spam. Have been using this since my first WP site in 2009 and would recommend it to everyone!
Used to get 1-2 spam postings per day. Haven't gotten a single one since I installed WP Captcha-Free. I may be targeted by mostly unsophisticated spammers, but this plugin certainly curbed my spam infestation. Super easy install. Highly recommended. Many thanks to the author.
I stumbled on this a while back and installed it in two WordPress sites I use. It keeps out almost all spammers, and without any captchas to worry about. I love it!
Since I installed it, I hardly receive any spam any more. And the little rest that comes through, is filtered by Akismet.
However, since there is only once in a while something in the Spam folder, it is easy now to actually read these "comments" and make sure, that no real comment gets deleted accidentally.
You want a spam filter to knock out all the spam but never stop a genuine comment. WP Captcha-Free has knocked out all the spam I was getting, and when I've tested it several times myself or via a friend, the comments were accepted no worries. So it seems to be working perfectly, but of course I can't know for sure if any genuine comments are being stopped.
It is quite invisible to the user, the only thing you notice is a slight delay in a comment being accepted.
I think it's brilliant.
Update: 1 year later, I'm still immensely happy with this plugin!!!