To contact other members on the site, simply go to the users profile and click the "Contact" button. You will be given a form that you can send messages via e-mail to the user.

The only thing is

You need to edit your profile and turn on your contact form if you want other users to be able to reach you. It is turned on by default for new users but it is off by default for the Volcano Boy users. Just click "My Account" over there on the left and then click "Edit", scroll down a bit and check off "personal contact form" under contact settings.

There's a guestbook there also if you want to say something publicly to the user.