Does anyone know how I can get a list of products belonging to a specific category from within a view file in Magento?

+2  A: 

It all depends on which view you're in. ;-)

First off, I hope you stayed within your template set (default in my example).

Use this as an example:

$_cat         = $this->getCurrentCategory();
$_parent      = $_cat->getParentCategory();
$_categories  = $_parent->getChildren();

/* @var $category Mage_Catalog_Model_Category */
$collection = Mage::getModel('catalog/category')->getCollection();
/* @var $collection Mage_Catalog_Model_Resource_Eav_Mysql4_Category_Collection */
    ->addAttributeToFilter('is_active', 1)
    ->setOrder('position', 'ASC')

$productCollection = Mage::getResourceModel('catalog/product_collection');
$layer             = Mage::getSingleton('catalog/layer');
// $productCollection should be ready here ;-)

I'm using the above code to display sister categories in my template - it's not ideal but it works.

It's sort of a hack because I did not yet have time to learn all the layout XML madness. Otherwise if you use the XMLs you need to keep in mind - it all depends on where you are at. Where means the template file and essentially also the layout (in terms of app/design/frontend/default/default/layout/*).

I know it's not much, but I hope it helps to get you started.