Get Base Url :
Mage::getBaseUrl();
Get Store Url : 
Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_WEB);
Get Skin Url :
Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_SKIN);
$this->getSkinUrl(‘images/imagename.jpg’);
Get Media Url :
Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA);
Get Js Url : 
Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_JS);
Get Current Url
Mage::helper(‘core/url’)->getCurrentUrl();
Get Home Url
Mage::helper(‘core/url’)->getHomeUrl();