Client-side javascript blocks all spam bots. XHTML 1.1 compliant. Now with support for WordPress Versions 3.1+
To install WP Hashcash, please download the plugin and unzip it, then copy the wp-hashcash.php file to wp-content/plugins. Activate the plugin and drag into your Widgetized sidebar for public statistics, or visit Options, WP Hashcash from the admin panel to configure options.
If you are upgrading from a previous version of WP-Hashcash, please disabled the plugin, then delete its files entirely. Then, upload the latest plugin files and activate!