How to display form module in two coloms?
You can use the markup-type in your form array to group form items and then style the groups.
The code below will wrap the three items with a div which has the class column-left. Do the same for the right column.

To clear things up: The column_left-item is of the type markup, which is the default type.

$form['column_left'] = array(
    '#prefix' =&gt; '&lt;div class="column-left"&gt;', 
    '#suffix' =&gt; '&lt;/div&gt;',
);
$form['column_left']['first'] = array(
    '#type' =&gt; 'textfield',
    '#title' =&gt; t('First name'),
    '#maxlength' =&gt; 20,
    '#required' =&gt; TRUE,
);
$form['column_left']['last'] = array(
    '#type' =&gt; 'textfield',
    '#title' =&gt; t('Last name'),
    '#maxlength' =&gt; 20,
    '#required' =&gt; TRUE,
);
$form['column_left']['street'] = array(
    '#type' =&gt; 'textfield',
    '#title' =&gt; t('Street Address'),
    '#required' =&gt; TRUE,
);


For Drupal 7, you can use the container-type and use the attributes array to add the class. A div is generated automatically.

$form['column_left'] = array(
  '#type' =&gt; 'container',
  '#attributes' =&gt; array(
    'class' =&gt; array('column-left'),
  ),
);