I just installed the reCAPTCHA WordPress plugin. It works like similar CAPTCHA plugins, but with a literary twist. From the reCAPTCHA website:

Over 60 million CAPTCHAs are solved every day by people around the world. reCAPTCHA channels this human effort into helping to digitize books from the Internet Archive. When you solve a reCAPTCHA, you help preserve literature by deciphering a word that was not readable by computers.

Now you can take part in preserving literature by commenting on this post! Let me know if you have any problems using reCAPTCHA.