Easy Speak’ Widget Contact Form is a plugin by Luke Roberts that utilizes a wordpress widget and jquery to create a widgetized contact form that visitors can use to send the site owner, or whoever you decide for that matter, email without the need to refresh or navigate from the page. This plugin has been updated to allow you to add an infinite number of input fields so the simple contact form could become a questionaire or quiz.
The plugin has been updated to check the email address is formatted correctly to try and reject spam!
You don’t need to use the widget provided by this plugin, You can use the plugin to install jQuery for you!
Download and info: http://wordpress.org/extend/plugins/easy-speak-widget-contact-form/
There is a related plugin: http://wordpress.org/extend/plugins/easy-speak-mailing-list/