You might try dCoda's wp_contactme:
http://www.dcoda.co.uk/index.php/tag/wp_contactme/
I've used it and liked it.
Some of the features (from the documentation):
Easy to add to post and pages with BBCode.
Easy to add to a sidebar with a widget.
Easy to add anywhere in a template with a function call.
Comes ready configured with a standard Contact form.
Has HTML/PHP templates to allow you to customise the form to collect what information you like.