Create posts on user registration

You kind of answered the question yourself already,

Create a function that will create the 3 posts ex:

function create_new_user_posts($user_id){
        if (!$user_id>0)
                return;
        //here we know the user has been created so to create 
        //3 posts we call wp_insert_post 3 times.
        // Create post object
        $my_bio_post = array(
             'post_title' => 'bio',
             'post_content' => 'This is my post.',
             'post_status' => 'publish',
             'post_author' => $user_id
        );

        // Insert the post into the database
        $bio = wp_insert_post( $my_bio_post );
        $my_portfolio_post = array(
             'post_title' => 'portfolio',
             'post_content' => 'This is my post.',
             'post_status' => 'publish',
             'post_author' => $user_id
        );

        // Insert the post into the database
        $portfolio = wp_insert_post( $my_portfolio_post );
        $my_contact_post = array(
             'post_title' => 'bio',
             'post_content' => 'This is my post.',
             'post_status' => 'publish',
             'post_author' => $user_id
        );

        // Insert the post into the database
        $contact = wp_insert_post( $my_contact_post );

        //and if you want to store the post ids in 
        //the user meta then simply use update_user_meta
        update_user_meta($user_id,'_bio_post',$bio);
        update_user_meta($user_id,'_portfolio_post',$portfolio);
        update_user_meta($user_id,'_contact_post',$contact);
}

and you hook that function using user_register hook

add_action('user_register','create_new_user_posts');

Update
When you hook a function to user_register the function receives the user id so you can use that to get whatever information you want about that user ex:

$user = get_user_by('id', $user_id);

and now $user is a USER object so you can change the post title to user the user info ex:

'post_title' => $user->user_firstname . " ". $user->user_lastname . 'bio'