[PhilJ]

Anyone wanting to easily add a Facebook 'Like' button...

In skin/smart_template/custom/common.tpl

At the end, insert...

 
<meta property="og:title" content="{$product.producttitle|default:$product.product|escape}" />
<meta property="og:site_name" content="{$config.Company.company_name}" />
<meta property="og:image" content="{$product.image_url|default:$product.tmbn_url}" />

Then in skin/smart_template/customer/main/product_details.tpl

After...

 
<div class="ask-question">
{include file="customer/buttons/button.tpl" button_title=$lng.lbl_ask_question_about_product style="link" href="javascript: return !popupOpen(xcart_web_dir + '/popup_ask.php?productid=`$product.productid`')"}
</div>

Insert...

<iframe src="http://www.facebook.com/plugins/like.php?href={$php_url.url|escape:"url"}&amp;layout=standard&amp;show_faces=true&amp;width=450&amp;action=like&amp;colorscheme=light" scrolling="no" frameborder="0" allowTransparency="true" style="border:none; overflow:hidden; width:450px; height:30px; margin-top:10px"></iframe>

Then run cleanup.php

Source | Demo

I don't have a Facebook account, so I can't test it personally