I used this trick to create a previous post link. Basically you just generate the previous posts list where you start hiding items after you have displayed the first item. This method generates valid HTML and allows you to set an accesskey which only accesses the first (visible) item.
<BloggerPreviousItems> <a href="<$BlogItemPermalinkURL$>" accesskey="v">Previous:<br><$BlogPreviousItemTitle$></a> <div class="hide"><![CDATA[ </BloggerPreviousItems> <div class="hide">]]></div>
Update 2005-09-01: Changed ‘next’ to ‘previous’ because it makes more sense this way.