Thanks for the suggestions. 
 
If I go with php code since I only really need this on one site for now, would this be the correct syntax. I'm not a php wizard.
	<?php if(is_category("acne-skin-care-treatment")): ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image1.jpg"></a>
	<?php elseif(is_category("acne-skin-care-treatment")): ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image2.jpg"></a>
	<?php elseif(is_category("lip-plumper")): ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image3.jpg"></a>
	<?php elseif(is_category("natural-skin-care")): ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image4.jpg"></a>
	<?php elseif(is_category("stretch-mark-prevention")): ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image5.jpg"></a>
	<?php elseif(is_category("sunless tanning")): ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image6.jpg"></a>
	<?php else: ?>
	  <a href="http://sponsorlink.com" ><img src="http://link/to/image7.jpg"></a>
	<?php endif; ?>
Simon, thanks for the link to widget logic. I might have some uses for that. 
