How do I put registration form in panel in Drupal 7
fucntion YOURMODULE_block_view($delta = ''){
  switch($delta){
    case 'YOURBLOCKNAME':
    $block['content'] = drupal_get_form('user_registration_form');
    break;
  } 
}


Or if you want to theme the block first, then register a theme hook in YOURMODULE_theme().

function YOURMODULE_theme(){
  $return['custom_user_reg']= array(
    'render element' =&gt; 'form',
    'arguments'=&gt; array('form'=&gt; null),
    'template' =&gt; 'templates/form--user-registration',
  );
  return $return;
}

function YOURMODULE_block_view($delta = ''){
  switch($delta){
    case 'YOURBLOCKNAME':
    $form = drupal_get_form('user_registration_form');
    $block['content'] = theme('custom_user_reg', array('form'=&gt;$form));
 }


Then in form--user-registration.tpl.php:

print render($form['email']);
print render($form['name']);
print drupal_render_children($form);


Of course you can add as much html in your tpl file as you want/need.