Magento 1.7/1.8: How to Join Collection to Table

The following works.
I've come up with this based on the way magento sorts a product collection based on an attribute that has options. see more details about this in Mage_Eav_Model_Entity_Attribute_Source_Table::addValueSortToCollection and Mage_Eav_Model_Resource_Entity_Attribute_Option::addOptionValueToCollection

//===>configure the fields below based on your needs
$attributeCode = 'vendor_id'; //replace this with the attribute code that holds the vendor
//get the attribute object
$attribute = Mage::getModel('eav/config')->getAttribute('catalog_product', $attributeCode);
//attribute id
$attributeId = $attribute->getId();
$tablePkName = 'vendor_id'; //primary key name of the vendor table
$nameField = 'name'; //vendor table name field - the one you need
//get table that holds the vendors
$table = Mage::getSingleton('core/resource')->getTableName('vendor/vendor');
//<=== end of configuration
$collection = Mage::getModel('catalog/product')->getCollection();
//add the vendor attribtue to select
$collection->addAttributeToSelect($attributeCode);
$valueTable1    = $attributeCode . '_t1';
$valueTable2    = $attributeCode . '_t2';
//perform 2 left joins in case the attribute has the scope website or store view. 
//It works even if the attribute has the scope global. this covers all the cases
$collection->getSelect()
    ->joinLeft(
        array($valueTable1 => $attribute->getBackend()->getTable()),
        "e.entity_id={$valueTable1}.entity_id"
            . " AND {$valueTable1}.attribute_id='{$attributeId}'"
            . " AND {$valueTable1}.store_id=0",
        array())
    ->joinLeft(
        array($valueTable2 => $attribute->getBackend()->getTable()),
        "e.entity_id={$valueTable2}.entity_id"
            . " AND {$valueTable2}.attribute_id='{$attributeId}'"
            . " AND {$valueTable2}.store_id='{$collection->getStoreId()}'",
        array()
    );
$valueExpr = $collection->getSelect()->getAdapter()
    ->getCheckSql("{$valueTable2}.value_id > 0", "{$valueTable2}.value", "{$valueTable1}.value");
$optionTable   = $attributeCode . '_option_value_t1';
$tableJoinCond = "{$optionTable}.{$tablePkName}={$valueExpr}";
//join with the vendor table
$collection->getSelect()
    ->joinLeft(
        array($optionTable => $table),
        $tableJoinCond,
        array($nameField));

    $quote_collection = Mage::getResourceModel('sales/quote_collection')
        ->addFieldToSelect('entity_id')
        ->addFieldToSelect('subtotal')
        ->addFieldToFilter('customer_id', 5);
    foreach ($quote_collection as $quote) {
        $data = $quote->getData();
        print_r($data);
    }   

Or if you know which field you need, for example Subtotal:

$subtotal = $quote->getSubtotal();