Does your WordPress site need a contact form? Something more complex? Here are a few I recommend.

Formidable (I use the Pro version a lot but the free one is cool too.)
http://wordpress.org/plugins/formidable/

Gravity Forms (Paid) I've not used it but heard good things about it.
http://www.gravityforms.com/

Contact Form 7 - Easy to configure for most basic form needs.
http://contactform7.com
Shared publicly