functions.php

<?php

// Add social networks fields to aithor profil and author info box
add_filter('user_contactmethods', 'manoz_profile_fields');
function manoz_profile_fields( $profile_fields ) {
    $profile_fields['twitter']   = __( 'Twitter URL',   'textdomain' );
    $profile_fields['facebook']  = __( 'Facebook URL',  'textdomain' );
    $profile_fields['gplus']     = __( 'Google+ URL',   'textdomain' );
    $profile_fields['linkedin']  = __( 'LinkedIn URL',  'textdomain' );
    $profile_fields['dribbble']  = __( 'Dribbble URL',  'textdomain' );
    $profile_fields['pinterest'] = __( 'Pinterest URL', 'textdomain' );
    $profile_fields['instagram'] = __( 'Instagram URL', 'textdomain' );

    return $profile_fields;
}

?>

loop.php

<?php 
/**
 * Place this after your </article> tag (for exemple)
 * I use a custom fontello pack for the icons.
 * My icon classes are: <i class="icon-name"></i>
*/

// Author info box
$social_names = array( 'link', 'twitter', 'facebook', 'gplus', 'linkedin', 'dribbble', 'pinterest', 'instagram' );
$social_urls = array();

foreach( $social_names as $social_name ) {
    $link = get_the_author_meta( $social_name );
    if( !empty($link) ) {
        if(strpos($link, "http") === 0) {
            $new_url = 'http://' . $link;
        }
        $social_urls[$social_name] = $link;
    }
} 
?>

<div class="author-infobox">
    <?php echo get_avatar( get_the_author_meta( 'ID' ), 60 ); // 60 is the avatar size ?>
    <div class="author-description clearfix">
        <h3><?php echo __( 'About', 'textdomain' );?> <a href="<?php echo get_author_posts_url( get_the_author_meta( 'ID' ) ); ?>"><?php the_author(); ?></a></h3>
        <?php if ( !empty( $social_urls ) ) { ?>
            <div class="author-social">
                <?php echo '<ul>'; ?>
                <?php
                    foreach ( $social_urls as $social_name => $social_url ) {
                        echo '<li><a href="'.$social_url.'"><i class="icon-'.$social_name.'"></i></a></li>';
                    }

                 ?>
                 <?php echo '</ul>'; ?>
            </div>
        <?php } ?>
        <p><?php the_author_meta( 'user_description' ); ?></p>
    </div>
</div>

style.css

/* Some style for the author box */

/* Author info box
------------------------------- */
.author-infobox {
    padding: 20px;
    border: 1px solid;
    border-color: #e5e6e9 #dfe0e4 #d0d1d5;
    border-radius: 0 0 3px 3px;
    background-color: #fff;
}

.author-infobox img {
    float: left;
    margin: 0 10px 5px 0;
    border-radius: 2px;
    box-shadow: 0 1px 2px #999; /* Callback for old browsers */
    box-shadow: 0 1px 2px rgba(0,0,0,0.5);
}

.author-description {position: relative};

.author-description h3 {
    margin-top: 0;
    font-size: 18px;
    font-style: italic;
    color: #aaa;
}

.author-social {
    position: absolute;
    top: 0;
    right: 0;
    font-size: 14px;
}

.author-social ul li {
    display: inline-block;
    vertical-align: top;
    zoom: 1; /* IE fix */
    *display: inline;  /* IE fix */
}

.author-social a {
    opacity: 1;
    -webkit-transition: opacity .2s;
    transition: opacity .2s;
}

.author-social a:hover {
    opacity: .4;
    -webkit-transition: opacity .2s;
    transition: opacity .2s;
}

.author-social a .icon-link      {color: #333333;}
.author-social a .icon-twitter   {color: #4B9CDB;}
.author-social a .icon-facebook  {color: #3b5998;}
.author-social a .icon-gplus     {color: #dd4c39;}
.author-social a .icon-linkedin  {color: #1b86be;}
.author-social a .icon-dribbble  {color: #ea4c89;}
.author-social a .icon-pinterest {color: #c42329;}
.author-social a .icon-instagram {color: #3f729b;}

C'est codé à l'aveugle donc pas testé mais c'est une piste d'optimisation