So your tired of always having to go through your catalog to add and remove products that have a special price to a certain category called On Sale or something similar. A solution is on hand now that will allow you to filter out those Special Priced products that have a special from and special to date.
First of all this is the code were that we're going to be using to do this.
<?php
Mage::getSingleton('core/session', array('name' => 'frontend'));
$_productCollection = Mage::getResourceModel('catalogsearch/advanced_collection')
->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
->addMinimalPrice()
->addStoreFilter();
Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($_productCollection);
Mage::getSingleton('catalog/product_visibility')->addVisibleInSearchFilterToCollection($_productCollection);
$todayDate = date('m/d/y');
$tomorrow = mktime(0, 0, 0, date('m'), date('d'), date('y'));
$tomorrowDate = date('m/d/y', $tomorrow);
$_productCollection->addAttributeToFilter('special_from_date', array('date' => true, 'to' => $todayDate))
->addAttributeToFilter('special_to_date', array('or'=> array(
0 => array('date' => true, 'from' => $tomorrowDate),
1 => array('is' => new Zend_Db_Expr('null')))
), 'left');
?>
<div class="listing-type-grid catalog-listing">
<?php $_collectionSize = $_productCollection->count() ?>
<?php $i=0; foreach($_productCollection as $_product):?>
<?php if($i++%3==0): ?>
<ol class="grid-row">
<?php endif; ?>
<li class="item">
<p class="product-image">
<a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($this->getImageLabel($_product, 'small_image')) ?>">
<img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image')->resize(135, 135); ?>" width="135" height="135" alt="<?php echo $this->htmlEscape($this->getImageLabel($_product, 'small_image')) ?>" title="<?php echo $this->htmlEscape($this->getImageLabel($_product, 'small_image')) ?>" />
</a>
</p>
<h5><a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>"><?php echo $this->htmlEscape($_product->getName()) ?></a></h5>
<?php if($_product->getRatingSummary()): ?>
<?php echo $this->getReviewsSummaryHtml($_product, 'short') ?>
<?php endif; ?>
<?php echo $this->getPriceHtml($_product, true) ?>
<?php if($_product->isSaleable()): ?>
<button type="button" class="form-button" onclick="setLocation('<?php echo $this->getAddToCartUrl($_product) ?>')"><span><?php echo $this->__('Add to Cart') ?></span></button>
<?php else: ?>
<div class="out-of-stock"><?php echo $this->__('Out of stock') ?></div>
<?php endif; ?>
</li>
<?php if($i%3==0 || $i==$_collectionSize): ?>
</ol>
<?php endif; ?>
<?php endforeach ?>
</div>
