I think I'm getting somewhere. The code below is from cart_offers.tpl - including this file on content.tpl doesn't display anything on the home page, but it's still active when the cart is loaded and it outputs the current active special:
{if $products and $cart.have_offers and $cart.applied_offers}
{capture name=dialog}
{foreach name=offers from=$cart.applied_offers item=offer}
{if $offer.promo_checkout ne ""}
<div>
{if $offer.html_checkout}
{$offer.promo_checkout}
{else}
<tt>{$offer.promo_checkout|escape}</tt>
{/if}
</div>
{if not $smarty.foreach.offers.last}
<div><img src="{$ImagesDir}/spacer.gif" width="1" height="30" alt="" /></div>
{/if}
{/if}
{/foreach}
{/capture}
{include file="customer/dialog.tpl" title=$lng.lbl_sp_offers_applied_to_cart content=$smarty.capture.dialog}
{/if}
The part I don't know how to do is to get the system to recognize $cart on the non-cart pages of the site. Any ideas???