AJAX Calendar is a plugin that will display an AJAXified WordPress calendar. This enhances the functionality of the standard calendar by:

• Allowing the asynchronous navigation of months, without updating the page
• Adding a drop-down list of post titles in each month (through the «-» button)
• Adding full caching support to reduce server load

More than that, it checks if all fields filled correctly, and also makes sure to avoid comment duplication, and has flood protection capabilities as well.

Probably one of the best ways you could spice up your WordPress Blog with AJAX; readers love it! Must see for yourself.

This plugin works well in all major Web browsers, and uses discrete AJAX. That means if JavaScript disabled, it’s using the original comment posting method.

Adds an AJAX rating system for your WordPress blog’s post/page.

Adds an AJAX poll system to your WordPress blog. You can easily include a poll into your WordPress’s blog post/page. WP-Polls is extremely customizable via templates and css styles and there are tons of options for you to choose to ensure that WP-Polls runs the way you wanted. It now supports multiple selection of answers.