I use the custom skin, and put some links near the top of the sidebar (line 215 in _main.php, for that skin). Here's what that looked like:

<div class="bSideBar">
	<div class="bSideItem">
		<h3><a href="http://www.link.com/">LINK TEXT</a></h3>
		<h3><?php $Blog->disp( 'name', 'htmlbody' ) ?></h3>

For wpc_default, it looks like the sidebar starts around line 143 (also _main.php), and you could play around adding the links wherever you want them - maybe line 148... the wpc skin is different than custom, so you'll have to experiment a bit to get it the way you like it.