From http://kahthong.com/2013/06/create-your-own-custom-drupal-block-programmatically

Creating a block

/**
* Implements hook_block_info().
*/
function YOUR_MODULE_block_info()
{
  $blocks = array();
	$blocks['YOUR_BLOCK_ABC'] = array(
		'info' => t('YOUR BLOCK NAME'),
		);
	return $blocks;
}

/**
* Implements hook_block_view().
*/
function YOUR_MODULE_block_view($delta = '')
{
	$block = array();
	switch ($delta) {
		case 'YOUR_BLOCK_ABC':
		$block['subject'] = '';
		$block['content'] = _YOUR_MODULE_BLOCK_ABC_CONTENT();
		break;
	}
	return $block;
}

function _YOUR_MODULE_BLOCK_ABC_CONTENT()
{
	$output = t('Hello world');
	return $output;
}