This is another popular question. Often you want to show items on a CMS page rather than a regular category page. But you still want to have the layered navigation to filter results like it appears by default with Magento at the category level (when listing products).
To add Magento’s layered navigation to a CMS page where you’re showing items simply edit your CMS page in the admin – under the “Design” tab put this code:
<block type="catalog/layer_view" name="catalog.leftnav" before="-" template="catalog/layer/view.phtml"/>
That will show the layered navigation at the very top of the left column on your CMS page. Of course make sure your CMS page layout is “2column with left bar” (under “layout” in the “Design” tab).