Add new Google+ field to WordPress profiles

functions.php

<?php
/*
 * Add Google field to WordPress profile
 * Kudos to Justin Tadlock
 * http://justintadlock.com/archives/2009/09/10/adding-and-using-custom-user-profile-fields
 */
// Display the new field
function werewp_googleplus_field( $user ) { ?>

	<h3>Extra profile information</h3>

	<table class="form-table">

		<tr>
			<th><label for="googleplus">Google +</label></th>

			<td>
				<input type="text" name="googleplus" id="googleplus" value="<?php echo esc_attr( get_the_author_meta( 'googleplus', $user->ID ) ); ?>" class="regular-text" /><br />
				<span class="description">Please enter your Google+ profile ID</span>
			</td>
		</tr>

	</table>
<?php }
add_action( 'show_user_profile', 'werewp_googleplus_field' );
add_action( 'edit_user_profile', 'werewp_googleplus_field' );

// Save Google+ field
function werewp_save_googleplus_field( $user_id ) {

	if ( !current_user_can( 'edit_user', $user_id ) )
		return false;
	update_usermeta( $user_id, 'googleplus', $_POST['googleplus'] );
}
add_action( 'personal_options_update', 'werewp_save_googleplus_field' );
add_action( 'edit_user_profile_update', 'werewp_save_googleplus_field' );

// Add paragraph with link to Google Profile, by inserting the function werewp_author_bio in your template files
function werewp_author_bio() {
	if ( get_the_author_meta( 'googleplus' ) ) { ?>
		<p class="googleplus">
			<a rel="author" href="https://plus.google.com/<?php the_author_meta( 'googleplus' ); ?>/about" title="Circle me on Google+">Circle me on Google+</a>
		</p>
	<?php }
}
?>