Add to All is a powerful plugin that will allow you to add custom code or CSS to your header, footer, content, or feed.
Bad Behavior complements other link spam solutions by acting as a gatekeeper, preventing spammers from ever delivering their junk, and in many cases, from ever reading your site in the first place.
Better Search replaces the default WordPress search with a contextual search including search results sorted by relevance.
Fast Secure Contact Form lets your visitors send you a quick e-mail message and blocks all common spammer tactics. Additionally, the plugin has a multi-form feature, optional extra fields, and an option to redirect visitors to any URL after the message is sent.