Magento Add Custom Breadcrumbs In custom Module.

Add following code in you modules block file.

public function _prepareLayout()
{
    $breadcrumbs = $this->getLayout()->getBlock('breadcrumbs');
    $breadcrumbs->addCrumb('home', array('label'=>Mage::helper('cms')->__('Home'), 'title'=>Mage::helper('cms')->__('Home Page'), 'link'=>Mage::getBaseUrl()));
    $breadcrumbs->addCrumb('an_alias', array('label'=>'Your label', 'title'=>'Your title', 'link'=>Mage::getUrl("your_module/your_block")));

    return parent::_prepareLayout();
}