Altering the text after a checkbox using the Drupal Form Api
You can give the $options as an array of value and label. And the label can then be given as a link using l().

'#options'       =&gt; array(
  'facebook'     =&gt; l(t('Facebook'), 'http://www.facebook.com'),
  'twitter'      =&gt; l(t('Twitter'), 'http://www.twitter.com'),
),