Adding a CMS block via setup script

For this, I suggest using the data folder of one of your custom modules.
Let's say that the module is currently at version 1.0.4.

Create the file data/[module]_setup/data-upgrade-1.0.4-1.0.5.php with the following content:

Edit: changed file name

$content = 'BLOCK CONTENT HERE';
//if you want one block for each store view, get the store collection
$stores = Mage::getModel('core/store')->getCollection()->addFieldToFilter('store_id', array('gt'=>0))->getAllIds();
//if you want one general block for all the store viwes, uncomment the line below
//$stores = array(0);
foreach ($stores as $store){
    $block = Mage::getModel('cms/block');
    $block->setTitle('Block title here');
    $block->setIdentifier('block_identifier_here');
    $block->setStores(array($store));
    $block->setIsActive(1);
    $block->setContent($content);
    $block->save();
}

After this just change the version in config.xml to 1.0.5 clear the cache and refresh any page.

Mage::app()->setCurrentStore(Mage_Core_Model_App::ADMIN_STORE_ID);

$staticBlock = array(
                'title' => 'Test Block',
                'identifier' => 'test-block',                   
                'content' => 'Sample Test Block',
                'is_active' => 1,                   
                'stores' => array(0)
                );

Mage::getModel('cms/block')->setData($staticBlock)->save();

From: http://blog.chapagain.com.np/magento-create-cms-page-static-block-programmatically/#sthash.1FYKYYhI.dpuf

Instead of using the sql folder, you should put any setup scripts modifying CMS data in the data folder. See app/code/core/Mage/Cms/data/cms_setup for some good examples. These install scripts add static blocks and CMS pages.

For changing config values, use this code:

$installer->setConfigData(
    Mage_Page_Model_Config::XML_PATH_CMS_LAYOUTS,
    'your_value_here'
);

Also, Here's a useful article